What else can I do with my medical laboratory degree?

To close out this year's edition of National Medical Laboratory Professionals Week, I want to step away from the hospital lab.

I left the hospital life a year and a half ago to move into an entirely different sort of laboratory work, but I still talk about the hospital every time I'm asked questions about the profession. I do it because it's the world I worked in the longest (so far) and so I know it very well, and because the majority of graduates from medical laboratory science programs will find employment in hospital labs. My information about working as a hospital med tech is relevant and well informed, but it's not the entire picture.

You can do a lot more than hospital work with a MLT or MLS degree. There are also positions available in walk-in medical clinics like LabCorp or Quest, and in some large medical practices. Some specialty medical practices, like endocrinology centers and fertility clinics, will also have their own small laboratory in-house to run some of the simpler tests. Often, in those places, a lab tech will end up doing more outside-the-lab work, like bringing patients into exam rooms, and taking blood pressure and other vital signs. Some of them are 24-hour places with shift work, and some are a 9-to-5 weekday job.

There are specialty laboratories that run all the weird complicated testing that other labs aren't equipped to do, like genetic testing. There are veterinary labs. Most manufacturers of food, cosmetics, and drugs will have laboratory staff to test their products for quality. There are labs that specialize in drug testing, for pre-employment screens or for athletes.

Depending on your interests, you can get yourself into a research laboratory at a university, or a place like NIH or the CDC. There are plenty of laboratories at the county, state, and federal level, also. Public health labs are the most obvious ones, but what about the FDA? EPA? Even the U.S. Geological Survey does a ton of microbiological research.

You can teach. You can travel and be a tech in other countries. You can get more technical and work for the instrumentation giants like Beckman Coulter or Siemens, either in tech support, sales, or research and development of new assays. If you like computers, you can get into programming and work with laboratory information systems.

And working for these companies doesn't necessarily mean you need to be sitting at a lab bench. Someone who's got a laboratory background can do very well in tech support, customer service and education, quality assurance, or regulatory compliance.

That's another area lab techs can move into - there are several regulatory bodies who oversee laboratories of different types. The American Association of Blood Banks, The Joint Commission, The College of American Pathologists - all of these organizations inspect laboratories for compliance and hand out accreditation, and need inspectors who understand laboratories.

Yes, when you graduate from a medical laboratory science program, you'll probably start out in a hospital lab, doing the shifts that the seasoned techs don't want. But you're not stuck there if you don't like it. It's been my experience that the school programs aren't very good at showing students all the other options that are out there, and how they can work towards them. Hopefully this post helps a few folks who are hating their night shift hematology job but don't know what else they can do with a medical laboratory degree.

Are There Any Questions? (Part 2)

How did you decide to enter this field?

I had a Bachelor's degree in Physiology and didn't get into graduate school on my first try, mostly because of a lack of practical research experience. I decided that the MedTech program would be a good way to earn some practical laboratory skills while I waited a year or two to apply again. I was surprised at how much I enjoyed the course material, though, and I ended up staying with the program and finding rewarding work in a hospital lab.

What kind of education and training did you have?

I already had a Bachelor's degree, and the MedTech program I graduated from was in a "CEGEP" in Montreal, which is similar to a US community college. While it was only a 3-year program, the Canadian Society for Medical Laboratory Scence (CSMLS) considers it equivalent to the 4-year college laboratory programs in other provinces. When I wanted to work in the US, my MedTech degree would have only been sufficient to let me sit for the MLT exam (Medical Laboratory Technician), but with my previous B.Sc. I could write the MLS exam and be a Medical Laboratory Scientist.

The final 6 months of that program were an unpaid internship shared between three area hospitals, where I worked 8-hour shifts in all the areas of the lab: hematology, biochemistry, blood bank, microbiology, and histotechnology. During that time, I got to work as though I were one of the hospital's regular employees, running patient specimens and reporting results. I was supervised and guided, of course, but after the first few days of training, I was mostly on my own and dealing with the workload as though I worked there for real.


What personal qualities are important for an individual considering this field?

Attention to detail is crucial, and an ability to detect when something doesn't seem right is a big plus. Sometimes a result might seem okay but in context it won't make sense - a good tech can sniff those out and deliver better care. For example, a really high glucose level might mean a diabetic patient in a crisis, but it could also mean that the specimen was drawn from the same vein a glucose IV is connected to.

Multitasking well is also helpful, because you're rarely just doing one thing. Most of the time, the laboratory staff is cross-trained to some extent, so that the tech running the urinalysis bench can go help the hematology tech if the workload is uneven. Especially on the off-shifts, where that type of "generalist" is much more common, you need to be willing and ready to be a team player. I know that gets thrown around a lot in the business world, but I think it's very true in the laboratory and I don't mean it in a dismissive corporate-speak way. The tests must get done, or patient care suffers. So if someone's getting backed up in their workload and you've got nothing to do, you get up, go over, and help. It's just what you do in the lab, because you care about those patients waiting for their results.

What do you wish you had known before entering this field?

The profession, while as vitally important to patient care as nursing, doesn't get very much respect. Few people know we even exist, let alone what we do, and our pay is much less than for nurses with equivalent education and experience. Unfortunately, this ignorance of our importance can sometimes exist within hospital management, and labs are often understaffed and overworked, with old equipment that can't be replaced due to budget cuts. We make do and we put up with it because we care about the patients upstairs in the OR or the ER or the maternity ward and want to do right by them.

That's why I care so much about Lab Week - I want to advocate for the profession so that we're more visible and our work is better understood. Without dedicated and caring laboratory staff, a hospital would fall apart.

What do you like best and find most rewarding about the career?

Knowing that every day, I did something to help a patient live longer or healthier by providing a doctor with a result, or preparing blood products for transfusion.

Now that I'm out of hospital work, I find I'm enjoying learning more about quality assurance as it applies to the laboratory. I'm doing more research and development work, and manufacturing FDA-licensed test reagents, and it's a lot slower-paced than when I was used to in the hospital. I like that I'm getting a chance to learn so many new things right now.

What do you like least and find most frustrating about the career?

Hospital politics and understaffing. It's hard to do a good and safe job when you're working on too many things at once.

How much influence do you have over decisions that affect you?

That depends on the specific lab and on the manager and supervisors. Good labs will ask for input before changing schedules, ordering new equipment, and adopting new procedures. In my experience, I have not had enough influence. That's part of why I took a break from hospital work (but being tired of evening shift was the main reason). I've never been very good at accepting "because that's how we've always done it" as an answer, and that sometimes gets me into trouble. I'm a problem-solver by nature, and I've always tried to improve processes by studying them first instead of just applying random fixes. While I think that hospital labs are starting to head in that direction, there's still a long way to go, and I often found myself frustrated when hospital management decided to "solve" a problem without really understanding it.

What additional training and qualifications are necessary for advancement?

There are levels of certification. MLT and MLS are the most common ones, but you can also take special courses for advanced certification in one specialty like chemistry or blood bank, and that is often a good path towards management. It's also possible to branch out from the hospital lab and work in other fields like quality assurance, manufacturing, instrumentation, and IT.

What specific advice would you give to someone entering this field?

Don't cut corners, ever. You have lives in your hands. Quality control is done for a reason. Procedures are in place for a reason. Don't ever let anyone else (nurses, doctors, management) bully you into cutting corners, either. Be prepared to work hard and probably not get a ton of kudos for it. I enjoyed the satisfaction of knowing the difference I was making, and I enjoyed the pressure and the feeling of being needed. It can be an incredibly draining career, but worth it if you want to be in healthcare and prefer working in a lab instead of directly with people. Oh, and if you're easily grossed out, or if you tend to faint at the sight of blood, this is obviously not a career for you.

Are There Any Questions?

Over the past few months, I've been preparing for Lab Week by collecting questions from my friends and readers about laboratory work. I've done my best to be honest, because the point isn't to trick people into joining the ranks of Medical Laboratory Scientists by painting the profession in a prettier light than it deserves. I love what I do, and my goal is to educate folks on what I mean by "what I do," and how I got there. If that inspires anyone to look into laboratory work as a career, that's an excellent bonus, and I encourage those folks to pipe up with any other questions they may have.


What sort of school is required for the job (in the US)?

That's a tough question, because "the job" can mean a few different things, and different schools handle Medical Laboratory programs differently. Most hospitals prefer to hire people who are certified by the American Society for Clinical Pathology (ASCP), so if you're considering a laboratory career, their website is a good place to start. This link will bring you to their certification section, where you can look into the various requirements to sit for the exams and earn a certification. There are several different certifications, and several ways to qualify for them, depending on your level of education and experience. In a nutshell, you qualify for certification as a medical laboratory technician (MLT) with an associate's degree, and a medical laboratory scientist (MLS) with a bachelor's degree. The difference between the two, in practical terms, varies a lot. Many employers will give an MLS a higher salary than an MLT, reflecting the extra years spent at school, but some places don't bother to differentiate between them. If you're looking to move up into management, keep in mind that most places will require the higher degree for supervisory or charge positions. You can also choose to certify in only one sub-specialty of laboratory science, like biochemistry or microbiology, but that will limit the areas you can work in, and all the schools I know of prepare you for the "everything" exams.

At school, you'll learn chemistry and biology and math and physiology, with a little bit of computer stuff and instrumentation thrown in. In my limited experience, a bachelor's level program will go deeper into the why and how of laboratory testing, but a graduate of a 2-year program is no less equipped to do the actual work. There are sit-and-take-notes classes, of course, but also many hours spent in the school's labs, learning techniques. Hospitals sometimes donate their older equipment to Medical Laboratory Science programs, so students get a chance to work with the instruments instead of just learning things theoretically. See if the school you're applying to has an internship program, or if you need to find work experience yourself. Internship programs are great because you get a feel for what the lab is really about, and employers get a free trial of you as an employee, so there's a chance you'll get a job offer out of it if you impress them.

Is it a good long-term job, or do most people get into it temporarily on the way to something else?

I think it's a great long-term job because of the job security. The laboratory workforce is aging, and there aren't enough new techs graduating to fill the positions left open when people retire. Hospitals are doing their best to cut back and make do with fewer techs, but the fact remains that someone's got to run the laboratory if the hospital is going to provide decent health care, so laboratory personnel aren't going to be downsized out of existence.

I'm happy that I made this career choice mostly because of the built-in flexibility. Because hospital laboratories are running 24 hours a day and never close, there are an incredible number of schedules to choose from. There are usually three shifts - days, evenings, nights - and some hospitals even have some swing shifts that fit somewhere in the middle. You can work full-time or part-time. You can work only weekends. You can be "PRN" (which means "as needed") and get called to fill in gaps in the schedule when people are sick or on vacation.

Not everyone shares my opinion about how good a career choice it is. Unfortunately, the pay for most Medical Laboratory Technicians and Medical Laboratory Scientists is far less than for comparable healthcare professions, like radiology techs, nurses, and pharmacy techs. Here's the most recent data from the US Bureau of Labor Statistics. Because of the lower wages, it's difficult to keep ambitious and talented young people in the field. Many younger techs I've worked with have used the laboratory as a part-time job while they go back to school to pursue advanced degrees in the hopes of moving into nursing or pharmacy. Let's just say that the med techs who stick with it long-term are definitely not in it for the money.

How much continuing education do you have to do? How well does your employer support it?

To maintain my MLS certification with ASCP, I need to complete 36 education credits every three years, spread across different areas of laboratory work. ASCP offers some online activities to help me earn credits, but unfortunately most of them aren't cheap. I try to look for free educational activities through vendors and other professional organizations. There are several ways to earn credit, including attending college classes, publishing a research paper, serving on committees, or attending lectures. The amount that an employer will chip in for educational activities varies a lot - education is often one of the first casualties of a shrinking budget. I've heard that some hospitals are very diligent about keeping their techs certified and helping track their education credits, but I've been more or less on my own so far.

If you're employed outside of the hospital world, certification maintenance is less important. Of course, keeping up on developments in your field of work is a good idea either way.

How much of your work deals with software?

Laboratory computer systems are interfaced with the hospital's information system so that tests can be ordered and reported electronically. Especially in hematology and chemistry, tests are mostly run on large analyzers which are hooked up to the computer system, so the techs only need to accept results on a screen before they send them on their way. You definitely need to be comfortable with learning how to work with new software if you're going to work in a modern lab, because the instruments all have their own operating systems, and most of your day will be spent ordering and reporting tests on computer screens. The more you can learn about how to make the instruments do what you want, and how to fix little issues that arise, the less stressful your work shifts will be. Of course, none of that helps you when the computers crash and you need to do it all on paper...

Do you have to wear different levels of protective clothing depending on the test?

I'm always wearing gloves and a lab coat when I'm handling specimens, because it's safest to assume that every specimen may be positive for something infectious. Where I am right now, all the blood I work with has tested negative for all the bad stuff, but it's important to remember that only means "the bad stuff we currently know about and test for." Blood wasn't tested for West Nile virus or Hepatitis C twenty years ago, and I have every reason to believe that some new bloodborne disease will become an issue in the next few decades and I'll find out that all this blood I thought was "clean" may have in fact been exposing me to some new pathogen. So I glove up, always. Why take a risk?

On top of the gloves and lab coat, I sometimes wear a face shield or work behind a splash guard if I'm doing something that might cause splashes. Cutting open units of plasma and pouring them into a pooling vessel, for example. That gets messy, and I don't need plasma in my eyes. I've also got big insulated gloves to wear when I handle specimens frozen in liquid nitrogen.

What's the neatest/most unusual thing you ever found (if you can talk about it)?

I think it's pretty incredible that in many cases, I was the first person to know that someone had influenza, or herpes, or leukemia. Until I called the doctor with the result, it was a suspicion. Afterwards, it was a diagnosis. That sort of thing kept me very aware of how important the work is.
 

Life as a Rural Med Tech

My friend and professional colleague, Scott, graduated with me from a medical laboratory technology program in Montreal several years ago. Our careers started very similarly, with both of us being offered positions in big Montreal hospitals. Last year, though, Scott made the decision to move to a tiny Quebec town so remote that there aren't any roads connecting it to the big cities and you've got to arrive by plane or ferry. 

Because he believes strongly in the advocacy aspect of Medical Laboratory Professionals Week, Scott was happy to allow a chat to become an interview for my blog. He will be translating part of this post for use in his hospital's newsletter to celebrate Lab Week in the far north.

Scott, you currently work in a very remote area of Quebec. Why did you decide to leave your job in a big Montreal hospital to work where you are now?

Changing from a larger institution to a more remote smaller institution was driven by the idea that I could be more involved globally in all the different branches of med lab. Larger institutions tend to train technologists in one particular area while a smaller lab involves more cross-training. Also, the quality of life in a small northern community was key in my decision to head north.

Downtown "Scottsville"

Besides the view and the shorter commute, what are the biggest differences you've noticed in how the lab is staffed and run at the two hospitals?

In the larger institution I found that quantity, tests per hour, turn around time were very important markers in the running of the lab. Patients are one of a number of patients. In a smaller lab; patient care and quality tends to be of the utmost importance. The results produced from a smaller lab are those of a neighbour, friend, or someone from one of the villages served.

I currently have three co workers. Two medical technologists and one technician. The shifts are 8am-4pm/10am-6pm/1pm-9pm Monday thru Friday with one 8am-4pm shift on Saturday and Sunday. All other hours are covered by an on-call service that is shared by the three medical technologists. Therefore, I do on-call every three weeks. I would say I'm called in on average 2-3 times per week. Emergencies most of the time are chest pains, heart attacks. Most big cases are transferred to larger tertiary centers. We are very dependent on charter airplanes: we have two planes on standby most of the time to move people around.

Scott's winter transportation

Would you go back to a big hospital, now that you've seen what a small rural hospital lab is like?

It would be difficult to return to a larger institution. I am happy overall with the job in the smaller hospital. I think it has more to do with quality of life than the actual job. There are crappy things to working here and crappy things there. Right now there is less crap here than there. :)

The Montreal General Hospital

Do you feel like a bigger hospital, because of its volume, is less able to be careful? Are the results coming out of the lab more likely to be inaccurate?

Quality is a difficult thing to judge. I don't think that results would be inaccurate but larger institutions with increased automation and being driven by quantity might have more difficulty picking up on problems that arise. Both institutions follow quality control and quality assurance guidelines; but to use an analogy, Ferrari produces very high quality cars but only produces a few per year while Ford produces millions of cars with very good quality but not to the standard of Ferrari.

"Scottsville": Home to the Ferrari of hospitals

Speaking of automation, is the rural hospital equipped with older analyzers, or are you working with newer versions of the instruments?

 

Each institution chooses instruments based on needs. The larger institution had a higher volume and therefore required newer and more performing machines. The smaller hospital had instruments for the volume that is done and therefore they do tend to be a little older but still produce very good results. As an example, I saw a new instrument being offered by a biomedical company that could produce over 4000 test results per hour. In the smaller lab, an instrument of that size would be useless. The smaller institution requires more reliable, proven instrumentation.

He's really, really far north

You're in a very very out-of-the-way spot and depend on ferries to bring you supplies. Have you ever had problems getting reagents or blood for transfusion due to weather problems? What happens when an instrument fails and needs repair?

On a daily basis, we are very dependent on the weather. If the weather is bad, sometimes we cannot receive orders or send out specialized tests to other hospitals. We tend to check the weather on an almost hourly basis due to the rapid changes that can occur weather wise. One of the most important choices in my opinion for the lab when purchasing instruments in to purchase reliability. But in cases when things do fail, a med tech must be able to tinker with instruments with the assistance of over the phone tech support. We do carry a few spare parts but most are sent next day if needed. If an instrument has a major failure, service contracts guarantee that service technicians will come out and have a look. The smaller lab does allow me to get more hand on with repairs.

A ferry bringing food so Scott won't have to eat his neighbors

What attracted you to the medical laboratory field?

I enjoy the scientific aspect of the job. I had gone to school in Chemistry and enjoy the idea of being more pratical than theoretical in the medical lab field.

Once you started work as a med tech, did the work resemble what you'd imagined it to be, or was it a shock to move from school to the work force?

The largest mental adjustment was probably dealing with stressful real life situations as compared to fictious cases. As medical technologist, we see the good and bad of most if not all health cases that pass through a hospital. The training I was provided in school provided both a classroom setting and a practical setting to help bridge the gap between theory and work life. Also, an internship in the last few months of school helped to limit the shock. Of course, in real life work, things are not always ideal and you're always learning about new things, new ways, and improving yourself everyday.

Med lab reality can get pretty gross

If you could go back to a med tech program where students are just starting the basic classes, what would you say to them?

I would honestly ask them if they are truly dedicated to patient care. Are they willing to work odd hours, weird shifts, weekends, holidays? The lab, as any other health profession, involves thinking about others more than oneself at times. You have to be willing to be flexible and available because in the end it is to help someone in need.

In My Blood

In most other workplaces, a blood-spattered desk would be cause for a police investigation.

For me, it was just Friday.

Let's just say that if blood or other bodily fluids and excretions bother you, you probably don't want to pursue a career as a medical laboratory scientist.

But maybe you do want to pursue that path. Maybe you love medical science but aren't masochistic enough to put yourself through medical school. Maybe you love helping sick people but don't want to be anywhere near them while you do, because, frankly, they're a little needy. Maybe you love biology and lab work, but don't want to spend a lifetime begging for grant money to keep your cell cultures or graduate students fed. There's hope for you yet! Stay tuned to find out how you too can have a vibrant healthcare career!

I know, I'm a ridiculous infomercial, but I feel like it's my duty to promote my profession, because there are too few of us out there, and we're not well understood or respected. I want that to change. Everyone knows about doctors and nurses, but the third vital side of the healthcare triangle, the medical "techs", live in relative obscurity.

The Board of Certification for medical technologists here in the US changed things up a couple of years ago and tried to give us more respect by changing our title from "Medical Technologist" to "Medical Laboratory Scientist". It was a lovely gesture, but it didn't really help. I mean, I didn't get a raise or a talk show or anything, and I still get a blank stare and polite nod when I tell folks what I do. Although I think people picture a lab coat and some test tubes now, which is a little closer to right.

I write about my work sometimes on this blog, and last year, I wrote a series of posts here for Medical Laboratory Professionals Week. Some of them explain the science and techniques behind laboratory tests, and some of them are about my experiences in the various labs I've worked in. I would very much like to do that again this year as a way to raise awareness about the profession. I never heard about medical laboratory science careers until I was already through university with a Bachelors in Physiology and couldn't find much to do with it. I hope that by writing about it here, I can make the profession just a little more visible, and maybe inspire someone to look into it as a career.

Even if I can't inspire anyone to get into a lab career, maybe I can help people understand what the job is about. Why do you only have to fast sometimes before a blood test? What happens to a blood donation? How does blood tell the doctor how sick someone is? I'd love to make Medical Laboratory Professionals Week into a sort of Q&A session, but for that I will need your help. Does anyone have any Qs that I can A?

What do you think the job is? Have you ever heard of it before? What would you like to know about labs, blood, and medical tests? I'm getting started early this year because I want to collect questions and get to work answering them well. I want to give myself time to draw diagrams and take pictures and maybe even interview folks in different types of lab positions, so I can really do right by my profession and show off my colleagues as the caring, intelligent, dedicated people they are.

So, hit me with your questions, and I'll do my best.

Plate it out

This is the 22nd of my "Advent Calendar" Christmas ornament posts. For some background information about this project and why I'm challenging myself to complete it, see here.

This week, I got a brand new ornament for my tree. My friend Natasha, who sent it, also contributed a great guest post for my blog, explaining why she bought it for me. When she saw it, she was reminded of me, and of microbiology, and thought it would be a nice way to connect us across a distance. I am very touched by the gesture.

But... it's wrong.

Not that Natasha chose badly, of course. I love it for what it is and what it represents. But the pattern on the petri dish, as pretty as it is, would flunk that artist right out of med tech school.

Microbiology is different from some of the other laboratory sciences, because it's about identification more than about quantitation. When you get a blood test done, you're getting a count of types of cells, or a measurement of the concentration of cholesterol or iron you've got in your body. With microbiology, it's a murder mystery, a whodunit. The aim of the game is to label the bug that's giving you trouble, so the doctor can deal with it properly.

I'll get into the details in a later post (I promise) but you should know that when bacteria are put onto tasty food like what's in a petri dish, they grow like crazy. Each individual cell stays in one spot and divides like mad, making a little spot. When you have a ton of bacteria, the spots smush together into a smear of goo. To identify the bug, we need a pure colony. Which means a spot that was made by one original bug, isolated from all the rest. We need to spread out the specimen so thin that we're planting single bugs at a time. That's not easy.

We use a technique of "streaking" across the quadrants of the plate. 

Image courtesy Wikimedia Commons

The idea is to smear a little bit of specimen on the plate, then use a new, sterilized tool to drag a tiny amount of it over to the next quadrant. By the end, you're dragging thinner and thinner concentrations of bacteria across the plate, and you'll get isolated colonies that you can then run tests on.

So, while the ornament gets the gist of it, I suspect it was created by an artist who was inspired by the beauty of microbiology, rather than a microbiologist who was moved to create art. Watercolor isn't the best way to go if you're trying to recreate the streaking pattern. A thick paint, dragged across the page like you'd do with the bacteria, would probably be more accurate.

But that doesn't mean I love it any less.

It’s Kind of Like They’re the Mary-Kate & Ashley Olsen of Christmas Ornaments

Note: Because I skipped a day of the Ornament Advent Calendar, and because I received a beautiful new ornament as a Christmas gift this week, I am doubling up on today's posts with the help of my good friend Natasha. She wanted to write a piece about the ornament she sent me, to explain the motives behind her choice. Here is her guest post. I'm going to call it post #21. My post about the ornament will be up later today, and will be #22.

Ornaments! Left: Natasha Right: Jen

You know what I mean. Fraternal twins that look so much alike you wonder if they’re identical. But if you look hard enough, you can see the differences.

Admittedly, our ornaments are more obviously different than some of those twins. Jen’s ornament is dark blue on dark blue. My ornament is dark blue on light blue. Totally different.

The pattern on the ornaments is the same though, and that’s most of what matters here. For most people, this pattern is just some strange streaks down the left side. However, once I laid eyes on it, I knew Jen had to have it for the pattern. And so did I.

See, that pattern is actually what makes these ornaments perfect. They’re little watercolors in petri dishes, so they’re already “sciencey” looking. But that pattern is a painting of how microbiologists isolate bacterial colonies. To isolate a single bacterial strain (thus, genetically identical), microbiologists or lab techs (HI JEN!) or students or whomever starts by streaking a big ol’ mess of bacteria from an old plate to a new one. Then, they sterilize their streaking implement (usually a metal tool called a loop) and draw a line through the heavy streak, and streak again a bit more wide-spread. Once you repeat that twice more, the last streak should result in not lines of colonies grown together, but isolated colonies that each resulted from a single bacterium. (Wikipedia has a great image. And about.com has a very clear write-up, if you want more details.)

I had to get this for Jen because she’s undoubtedly done this a million times. (I’ve probably only done this a half million or so.) Because she’s a total science geek, just like me. Because it’s beautiful in it’s own right, but there’s like a little secret hidden in the art if you’ve been there.

Because we have a similar background with a lot of shared experiences, and I realized this could give us a tangible link to those shared experiences that we mutually geek out about regularly.

I hope she takes it on that cruise she’s always talking about and shows it off.

Natasha and I are long-time Internet buddies. We try to get together in reality sometimes, but we live far apart. Still, we talk a ton online, and I think we get along so well because we both like to geek out over stuff in our own ways. She runs a blog of her own, MetaCookbook, where she discusses food, science, and beer, and treats her readers to some fascinating blather along the way. I encourage you to check out her stuff. She's not a recipe blogger, and she's not a rabid granola foodie. She's just someone who loves food, from growing it to eating it to the communities it can build. She's funny and smart and real and I get mad at her when she leaves the blog un-updated for more than a week. That should be enough information to get you over there for a look! 

- Jen

Lab skills or life skills?

Considering how many hours I have spent working in laboratories, I suppose it was inevitable that lab experiences would begin to influence my everyday life.

The rinsing principle

Let's say I'm going to wash up a unit of red cells to use in a procedure. First, I have to cut the bag open and pour the blood into a big centrifuge bottle with some saline solution, which is a messy process. But no matter how hard I shake it, there are always some red cells left clinging to the inside surfaces of the bag. I want to get as much of that into my bottle as possible, so I squirt in some saline from a squeeze bottle and swish it around the almost-empty bag to get all the good stuff out.

This is a remarkably useful process to bring into real life. For example, when I get to the end of a carton of coffee creamer, I spoon some coffee into it and swirl the carton to clean off its insides, then pour it all back into my coffee cup. I've also been doing it with jars of spaghetti sauce, because I can never get all of it out, even struggling with a spatula. I dump the jar out onto one side of the pot of cooked pasta, then I scoop up some of the uncoated noodles, pop them into the sauce jar, shake it up good, and then dump the noodles back into the pot. Less waste!

Butt-operated doors

Gloves and door handles aren't supposed to meet, since gloves are potentially covered in nasties. I've developed a butt-first approach to swinging lab doors that really works for me. Back into the door, gentle shove with my butt, and I'm through. I do this more often in non-lab settings than I'd like to admit, probably to my husband's embarrassment. If the door has a lever-style handle, I can navigate that quite easily by adding my elbow to the procedure. I lean down, push with my elbow, and then bump the door with my hip to get through.

It's somewhat more complicated when the door opens towards me, but I've recently been practising and can often use my elbow to get the door opened wide enough to stick my foot into the opening and swing it the rest of the way. Very useful in public bathroom situations.

Regular round doorknobs have thus far remained beyond my skill level.

The microbiology grip

You're supposed to keep things sterile in microbiology, because one tiny mold spore or bacterium getting into your culture medium can ruin everything. That's why microbiologists do most of their work with their arms inside special biological safety cabinets whose airflow and HEPA filters minimize the possibility of contamination. Still, sometimes you've got to unscrew the cap on a tube of media you want to inoculate, and you can't just put it down on the desk. Solution: the Microbiology Grip.

It can be accomplished with the pinky finger of the dominant hand:

Pinky technique - image from eplantscience.com

Or, if one absolutely needs the strength or dexterity of the thumb and index fingers to unscrew the cap, one can try the claw grip, but the inoculation wire or loop ends up being held awkwardly, and I think there is less control with this method.

Claw-style - image from ndsu.edu

And where, you may ask, am I finding a use for such a grip? Toothpaste. Not because my sink is so disgusting that I don't dare put down a toothpaste cap, but because my hands just do it anyway. Muscle memory is no joke. I hold my toothbrush like an inoculation loop in my right hand, then pick up the toothpaste tube in my left, bring my hands together, and unscrew the cap by gripping it with my pinky and then twisting both hands in opposite directions. I keep the cap firmly in my pinky grip while I apply toothpaste to my brush, and then I recap the tube and brush my teeth.

Laugh at me if you wish, but I can be confident that there are no mold spores in my Crest Complete with Scope.

Is it the flu?

What a week. I felt a little lightheaded on Wednesday, which progressed to dull aches in my bones and a complete loss of appetite by lunch time. By the end of the work day, I had developed a deep, barking cough and a sore throat. Needless to say, my boss kicked me out early, trying to prevent the spread of whatever plague I was incubating in my lungs.

My trusty thermometer showed a slight fever, so I took some generic cough-and-cold medicine, hoping that the decongestant would help the sniffles and cough, and the acetaminophen would fight the fever. I spent the evening on the couch, coughing and sneezing and constantly shifting to get comfortable. My sleep that night was horrible despite the NyQuil I took to knock myself out - the drugs didn't seem to be doing anything at all, and I woke up at 5am with an even higher fever. I called work to tell them I'd be staying home, took more cough-and-cold stuff, and tried to sleep, but the back pain made it impossible to get comfortable. For a while I was concerned it might be my kidney stones coming back to get me, but the pain was in the wrong place for that, thank goodness.

Once the sun was up, I called my doctor's office, and they told me they would be able to squeeze me in that afternoon. In desperation to survive until my appointment, I switched to ibuprofen for the pain - miraculously, it worked. I slept until appointment time.

The official diagnosis? Not strep throat, and not influenza. Bronchitis, likely viral, is what she labeled me with, which is sort of a cop-out, because it just means I have irritated bronchial passages. Um, yeah. I've been coughing my head off for 24 hours. Trust me, if the bronchi weren't irritated, they sure are now. The good doctor told me to pick up some guaifenesin (in some types of Robitussin and Mucinex), then go home and sleep it off.

When I went back to work on Friday and reassured everyone it wasn't the flu, I was asked "how do they know that? Did they test you that quickly?" Yes, yes they did. Thankfully for public health and for pandemic monitoring, hospitals and doctor's offices have a rapid influenza test that can give you an answer within 15 minutes. This makes it easier to distinguish "just a cold" from "influenza", and track the spread of seasonal or pandemic flu.

How does the test work?

Rapid flu test, image from bd.com

First, a swab is stuffed up the patient's nose. Usually, it's a long Q-tip type swab, and it gets rotated in the nostrils a few times before being put back into its holder for the lab. The throat can also be swabbed, because flu viruses hang out in both areas. When the H1N1 influenza, or swine flu, was spreading, it was discovered that the highest concentrations of viruses could be found high in the nasopharynx, or the place where your nasal passage meets your throat, way up past your palate. That's a very difficult area to reach, so a different, flexible swab became the preferred collection method. Here's an illustration:

Nasophagyngeal specimen collection. Image from Stanford University Medical Center.

Yes, it's about as unpleasant as it looks. I can testify to that.

Once the swab gets to the lab, it's dipped into a cocktail of liquid reagents that will extract the flu viruses from the swab, and then the liquid is placed into small wells at the end of a test card. As the liquid moves across the card by capillary action, it passes through a zone, right near the wells, where antibodies against influenza antigens (particles) are embedded. The antibodies are tagged with colored molecules, so as you watch the liquid move across the card, it will look pinkish, or blue, depending on which manufacturer's kit you're using. The antibodies get dragged along whether or not they've bound any antigen - that's why every test has a control line and a test line, to be sure the antibodies are there and moving properly. 

The test line is a strip of the card coated with antibodies against the first antibody, so as the colored antibodies get dragged along, they will stick to that area. When enough of them congregate there, you see a colored line in the control area, meaning that the capillary action is effective and the test is working properly. The control line is a little different - it's got a set of antibodies against another part of the influenza virus, so if those color-tagged antibodies picked up any flu viruses at the start, this is where they'll get caught up, and make a colored line in the test area. If there are no flu antigens in the specimen, the liquid will pass on through and no labeled antibodies will bind here, so there won't be a line.

Almost every rapid test works in a similar way. Pregnancy tests, Strep tests, anything that involves a strip dipped into a liquid specimen, or drops on a card - they all work on the same principle. The antigen, whether it's a virus (flu, mono), bacterium or bacterial toxin (Strep, C. difficile), or hormone (hCG for pregnancy tests, LH for ovulation tests), travels along a card and gets picked up by labeled antibodies, and then trapped along a test line so we can see it.

Isn't science great?

Now if only they could cure non-influenza viral respiratory infections with a magic pill!

Antibody Cake!

To round off a week's worth of laboratory stories, how about some dessert? I know you must be hungry, because I didn't even tell you anything about microbiology and the fun specimens that come into the lab.

My contribution this week was a cake for my coworkers. I went with Funfetti cake, because in my experience nobody hates Funfetti, and it was easier for me to use a box mix than to try my hand at a from-scratch cake. I colored some vanilla frosting so it would have a yellow tint like the plasma we work with, and then I decorated it with antibodies.

I initially thought pretzel sticks would work, but they're too inflexible. My antibodies are made out of Twizzlers Pull-and-Peel (cherry flavor), carefully peeled, cut to size, and pressed into the frosting. Several which were not cut to the right length were eaten in the process. For science.

The little guys around the edges are IgG molecules. They're made of two long "heavy chains" and two small "light chains" and look like little letter "Y"s. The upper tips of the Y, where the light chains and heavy chains are held together with sulfide bonds, is where the antibody magic happens in your immune system. Those tips will recognize and bind antigens, signalling your immune cells to attack. Variations in the amino acids at the antigen-binding region of the antibodies make your immune system capable of mounting a response to pretty much anything nature can throw at it.

The big mess at the middle is an IgM pentamer, which just means five IgM antibodies bound together into an immunological ninja star. IgM is usually the first antibody to respond to an infection. The reason you can be tested for Lyme disease and they can tell the difference between an active infection and a past infection is that the IgM will be present if your body is still fighting in its initial encounter with the bug, while the IgG antibodies will persist for life, hanging around ready to multiply if you're ever re-infected.

I'm pretty certain that cake doesn't have much effect on the immune system, but it sure made us happy.

Life in a manufacturing lab

My new lab is different: we're not getting patient specimens for testing, and we're not reporting results to doctors. We're a manufacturing lab, taking plasma, unsuitable for donation because of antibodies, and making a useful product out of it. It's an entirely different world from the hospital labs I started in, and I'd like to give you a window so you can peek inside. Here's an anecdote and a description of one of my tasks for you.

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One of our big pieces of equipment in the lab is a liquid nitrogen tank, where we keep rare cells, frozen in little vials. We need to go in and retrieve them for testing sometimes, depending on what project is underway, and nobody enjoys doing it, because it's cold in that tank. About -180C on average. We put on big blue gloves worthy of an Antarctic expedition, pop up the lid, and then reach in and pull out one of the vertical racks submerged in liquid nitrogen. Each rack has several shelves, and on each shelf is a little cardboard box containing a selection of vials. We have to pull out the rack, lean it horizontally in the tank so it stays cold, then pull out the right box, tip it to pour out the liquid nitrogen, and then sit it on the tank edge to open it and pick out the right vial.

Of course, as I turned back to put the lid back onto the box of vials, I bumped the box with my clumsy blue gloves and then gasped as the box flipped over into the tank, releasing fifteen vials of valuable cells into the liquid below. First I yelped, then I cursed, then I sighed. Peeking into the tank, I could barely see through the fog created when the cold condenses the water vapor out of the air, but somewhere under the clouds I could see white caps bobbing at the surface of the nitrogen, daring me to reach in for them. Considering my limited options - human hands, even in big antarctic gloves, don't react well to immersion in liquid nitrogen - I went looking for my supervisor.

As it turns out, I wasn't the first to dump vials into the tank, but that didn't make me feel much better. My supervisor rigged a scoop out of a huge pair of pliers and a small sieve, and we went fishing. The floating vials came up pretty easily, but the others were more of a challenge, requiring some digging and scraping of the ice at the bottom to dislodge the vials that had filled with liquid nitrogen and gone down. We got them all, but not until after I knocked one back into the tank while trying to stuff it into the box. Lucky for me, my supervisor found this funny enough to almost choke to death, instead of being frustrated with his twitchy underling.

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When I've done everything right, the final product from weeks of effort is a huge glass vessel full of processed and purified serum - it can be up to 30 liters, but usually it's closer to 15 or so. It has preservative in it to prevent microbial growth, but nonetheless, It gets put through an extremely fine filter before we proceed to fill our final 3- or 5-mL product vials.

The vials are filled manually with the help of a small pump and a very coordinated tech who's able to aim the liquid into the vials one at a time, over and over, until they're all full. The filling is done in a fancy "clean room", which means that when I go in to help, I dress up like I'm going to tackle the Andromeda Strain. Fluffy blue hairnet, gloves, mask, hood, booties, and a giant set of white coveralls. Here's an example of the checklist I have to go through to make sure I'm fully covered up:

Those suits are made of a synthetic, plastic-like material so they don't shed fibers, which also makes them very warm! I'm glad I only need to put on the "bunny suit" every few weeks. It's not exactly a flattering look for me. We have a filling session once a month on average, and it can take almost a whole day for the bigger volumes. While we're in the room, we perform environmental monitoring to check for particles and bacteria or molds in the air, and we wipe everything down, especially our hands, regularly with alcohol foam. At the end of the process, we touch microbiology plates with our fingers to see if we did a good job staying clean. If anything grows, we're in trouble. 

As one person fills the vials, someone else puts caps on them and secures them gently. The vials sit snugly against each other, about 250 to a metal tray, so this part is tricky, especially with gloved hands slippery from alcohol gel. Outside of the clean room, we tighten the caps all the way, re-check the count, and then secure the product in a tamper-proof box or wire cage. At this point, the vials are unlabeled, and since a vial of plasma looks like a vial of plasma, we wouldn't be able to tell two products apart if we mixed them up. We keep everything apart and clearly labeled on the outside, and we make sure that the area is completely free of any other product before we take them from their secure storage to label and inspect them.

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It's so very different from what I was used to in the hospitals, and yet the concepts are the same. Quality control, attention to details, careful labeling - you'll see this in any lab you visit. While the context might change, and the products and results labs put out will vary, you can be sure the techs behind the work are referencing Standard Operating Procedures and following the rules. Because what we do matters, and we know it.

All you ever wanted to know about your urine sample

How much urine do you guys really need? Is it really so easy to contaminate urine?

How much we need depends on exactly why the doctor's making you pee in a cup. If it's for a pregnancy test, we need a few drops, but if it's to check for a urinary tract infection, we need more. Here's why.

When we receive the urine in the lab, it's often in a tube like this, and sometimes a second, smaller tube comes with it, for microbiology.

Obviously, for most of us, it's incredibly hard to pee into such a small target receptacle, so we're handed a cup to use instead. Using a fancy system of urine cups and vacuum tubes, the staff in the ER or doctor's office can transfer urine to a smaller, leakproof container for transport to the lab without ever having to open the cup and risk contamination. Not to mention that the big urine cups are notoriously leaky, which is gross.

The small tube contains 10ml, and that's what we'd ideally like to receive in the lab, because of what we're going to do with it.

The ER normally orders a "urinalysis" or a "urinalysis with microscopic examination". Both of those start off with a chemical analysis, sometimes done on an instrument that aspirates and tests samples on its own, and sometimes done with a manual dipstick. The dipstick has several raised pads, each of which is saturated with a chemical or dye that will react with a different analyte in the urine. 

The average dipstick will check for glucose, bilirubin, urobilinogen, ketones, specific gravity, blood, pH, protein, nitrite, and white blood cells. What does it all mean? 

Specific gravity tells you how concentrated the urine is, and it's very variable depending on how well hydrated a person is. The pH can be vary depending on diet. Bilirubin and urobilinogen can give some information on liver function. The presence of sugar and ketones can indicate diabetes - there shouldn't be sugar in the urine at all unless the blood sugar is very high, and the presence of ketones means that the body isn't able to metabolize sugars and is resorting to breaking down protein and fatty acids. Someone on a zero-carb diet will have ketones in their urine, but they won't have sugar. Protein is a bad sign, because the filtering apparatus in the kidney is normally too small to let proteins through. Proteinuria can be a sign of kidney damage or, in a pregnant woman, pre-eclampsia. Blood is not good to find either, because it can mean kidney damage, with red cells leaking from the blood all the way up in the kidneys, but it could also be from further down the line in the bladder or urethra, or can be a contaminant (when a menstruating woman provides a sample, for example). Nitrite and white cells, together, indicate an infection, because some bacteria produce nitrite as a by-product, and white cells will be around to fight the infection. Not all bacteria will make nitrite, though, so if it's negative you're not necessarily in the clear. That's what the microscopic exam is for.

Once we've done the dipstick test, we only proceed to a microscopic exam if it was ordered, or if one of the parameters on the dipstick test indicates its necessity. Abnormal blood, white cells, nitrite, protein, and glucose can trigger a microscopic exam. In lab-speak, we call this a reflex test, where the result of one test automatically triggers a second test. We centrifuge the specimen, pour off the liquid portion, and examine any sediment from the bottom of the tube. We put a drop on a microscope slide, and look for bacteria, red and white blood cells, and crystals. All this gets reported to the ER or the floor, and the doctor decides whether to order a microbiology culture on the second tube.

All this work requires a "clean catch" specimen, which is why you're handed a little cleansing wipe and told to let the first little bit of urine miss the cup before starting collection. That area of your body is notoriously bacteria-ridden, no matter how clean you think you are, and if the bugs on your skin get into the cup, it can look like you have an infection when you don't. Also, if epithelial (skin) cells cloud the urine, it's hard to look through the mess to find red cells that could indicate a serious problem. If there are too many epis (as we call them) in the specimen, we'll usually ask for a new one, because it's not going to be very useful. Obviously, the problem of blood cells contaminating a specimen of a menstruating woman is a pretty big one, but the doctors know that from the start. If it's extremely important to get a non-contaminated specimen, they can use a catheter and go straight to the bladder, which isn't fun for anyone!

Lab Week Q&A - Bar Codes

 Part two of yesterday's question was about bar code labels.

Wait, are the colors of caps consistent across labs? I seriously always just figured it was an internal thing, and the bar codes on the sides were the important parts of communicating info to other labs if blood had to be sent out there.

 

While the cap color is extremely important in blood collection, because the quality and usability of the specimen depends immensely on how it was collected and stored prior to testing, it doesn't tell the lab what tests to run. The bar code, tied into the Laboratory Information System (LIS), has that job. The way it normally works is that a test is ordered by a physician (usually physically entered into the computer system by a nurse or a member of administrative staff working at the nurses' station), the computer puts that information into a bar code format, which is printed out and brought to the patient's side so the blood can be drawn and the tubes labeled with those bar codes. The bar codes usually list the test and the approved tube color in human-readable language, which is helpful for the staff acquiring the specimens.

Once a tube gets to the lab, the bar code is scanned, acknowledging receipt of the specimen. This time stamp is important because hospitals take turnaround time, or the time it takes from receipt of the specimen to release of a result, very seriously. The scanning is sometimes done manually by an accessioning tech, and then brought to the appropriate area of the lab, but in most larger hospitals, tubes are brought to an automated track system, where they are scanned, sorted, centrifuged if necessary, and brought around the lab where they're sampled directly off the track without a tech ever needing to touch the tube.

Automated track system (Beckman Coulter)

An automated system like that is great for many reasons. It can improve the speed and throughput of the lab, because nothing needs to wait for a tech to bring it to the next instrument. It's good for safety, because any time you can eliminate contact between a person and a blood specimen, you've eliminated a chance of exposure to a bloodborne pathogen like HIV or Hepatitis B. It's got its drawbacks, however.

One big issue is that the instrument doesn't look at the tubes. It only sees bar codes. If a specimen somehow sneaks by without getting de-capped, the specimen probe on the instrument will smash into the cap, expecting a clear path to the serum. The probe has a liquid sensor, and only starts aspirating serum when it feels the top of the liquid. It's expecting the tube to be full - if it's a very short draw, there's a risk that it will keep going and suck up the gel separator in the tube, gumming up all the tubing in the instrument and shutting it down for cleaning. That's why our lab had this sign posted by the inlet of the automated track:

Inlet of the automated line, with warnings!

Also, because all the instrument knows is the bar code, if someone puts the wrong label on a tube, there's no easy way to know unless someone is very careful about checking every tube before it gets put on the line. Ideally, they would all get a check, but when the workload is very high, some can get missed. Normally a label error is immediately apparent, like when a lavender tube, which is supposed to be diverted to hematology, chugs along the track towards the centrifuge to be spun - it's easy to spot because it's shorter than the chemistry tubes. If it gets all the way to the instrument without raising suspicions, say, if a tall pink top is labeled with a Chem-7 bar code, the results will cause the tech to pull the tube off the line and have a look at it. The potassium will be so high as to be incompatible with life!

Bar codes make it easier for the lab staff, because it saves us the trouble of having to program all the tests in manually for every single specimen. It saves us a lot of time when the instrument can read the orders and get the tests done. However, when specimens are sent out to other reference labs for more esoteric testing, they can't read the barcodes produced by our internal computer system. We have to fill out paper requisition forms and then send the tubes off (or poured-off serum) in special packaging, sometimes on dry ice, sometimes at room temperature, whatever the reference lab requests. Some hospitals have the system computerized and can fill out online requisitions and print out reference-lab-specific bar codes for the specimens - because the reference lab will have their own computer system and won't be able to use the original bar codes. It's like our bar codes are in German, but the other lab needs them to be in Finnish. We can either give them all the information on paper and they'll make their own Finnish labels when they get the specimen, or we can use their software to do that ourselves. That requires a special arrangement between the two labs, and not everybody has the resources to do it.

Even with the help of the bar codes, we still need to order things manually sometimes when tests are added on later, or if tests need to be repeated, but the only time the lab does everything manually is when the computer system goes down.

Two bad things can happen with the computers. The hospital system can go down, or the lab system can go down. In our facility, it was two separate systems, so although they could speak to each other, either one could die independently, leaving us with two different kinds of messes. If the hospital system goes down, the floors send down the tubes with patient-information labels that look like the patients' hospital armband. They include a "downtime" order form where they can check off all the tests they want run. Then we can order the labs on our end, getting bar codes, sticking them over the other labels, and proceeding as usual. The instruments still know what to do, the results still come onto our computer screens for analysis, and we can call, or print out and fax, the results to the floors. That's tedious, but not terrible. When the lab system goes down, it's chaos. We log receipt manually and program tests manually. We keep reference sheets handy to confirm panic values and normal ranges, and we fend off calls from the floors asking why everything is taking so long. We keep piles of instrument printouts so we can later manually enter everything into the computer. Some instruments will allow you to re-send the data once the system is back up, but not all of them. We love bar codes and computers. Very, very much.

Lab Week Q&A - Color coded blood collection tubes

As much as lab week is about celebrating the work of laboratory professionals, I see it as an opportunity to educate people about what happens in a lab. You get blood drawn, and you get results back, but what happens in between? I hope that I do a good job explaining things - please let me know in the comments if there's anything I missed or that you'd like to know more about.

The question for today is:

Wait, are the colors of caps consistent across labs? I seriously always just figured it was an internal thing, and the bar codes on the sides were the important parts of communicating info to other labs if blood had to be sent out there.

I'm going to break this into two parts, about tube colors and bar codes, and address each one in a separate post. I'll start with the colors.

If you've ever had lab work drawn, whether at a doctor's office, a hospital, or an external collection site like LabCorp, you may have noticed that when they take more than one tube of blood, the caps on the tubes are usually different colors. That's because there are different requirements for how the blood is treated and transported before it gets tested.

Common tube colors - from bd.com

Cap color is indeed consistent across labs. More accurately, you could say that it's consistent among the major manufacturers of blood collection tubes. It's possible that the manufacturers are doing this voluntarily, but I suspect there may be a federal entity like the Food and Drug Administration (FDA) involved, since it could hugely affect patient safety. Even if there is no official rule about cap color in the Code of Federal Regulations, I suspect that someone trying to market an EDTA tube with a green cap would find a very grumpy FDA inspector on their case.

Now, EDTA (ethylenediaminetetraacetic acid) probably doesn't mean much to you, yet. I'm here to tell you that it's an anticoagulant, one of many, used in blood collection tubes. Depending on what test is being run, we want the blood to act in different ways. I'll go over the most commonly used tubes and explain what the cap colors mean and what sort of tests each type is normally used for.

Pink or Lavender - EDTA

EDTA tube - from bd.com

Both pink and lavender tubes contain EDTA, which is a chemical that binds with and ties up calcium ions. Because blood needs calcium ions present in order to initiate the clotting process, blood that is collected into a pink or lavender top tube (and well mixed) will remain liquid.

Lavender tubes are generally used for complete blood counts (often shortened to CBC), which includes things like white cell and platelet count, and hemoglobin. This makes sense - if we're trying to do a platelet count, we need the blood to remain liquid, since a clot is going to tie up a bunch of platelets. If a number of blood cells are tied up in a clot and unavailable for the instrument to count, then the count will seem a lot lower than it really is. A CBC is one of the most commonly ordered tests, because it can tell a doctor about infection (high white cell count) or anemia (low red cell count), which are common reasons for doctor visits. You're very likely to have a lavender tube drawn if you're getting lab work done.

The main difference between the two colors is that the pink top tubes are generally bigger, and get spun down in a centrifuge to separate the plasma from the cells. The pink tubes are primarily used in the blood bank, because we run tests on both the cell part and the plasma part of the blood. We could use lavender top tubes, but we like to have a bigger volume of specimen to work with, in case we need to start cross-matching blood for the patient, which will use up the plasma. Also, the rules for labeling blood bank specimens are usually more strict, and having a bigger tube leaves more room to write out the patient's information.

Light Blue - Sodium Citrate

Sodium Citrate tubes - from bd.com

Blue top tubes are used primarily in coagulation studies, like monitoring heparin or warfarin therapy, or looking for clotting disorders before a patient goes to surgery. Sodium citrate, like EDTA, also prevents clotting by tying up calcium ions, but it's better than EDTA in preserving the rest of the blood's clotting factors. The tubes are always the same size, and contain a set amount of sodium citrate. Most coagulation tests start by adding some calcium back in and seeing how long it takes for the blood to clot, so it's extremely important to fill the tubes all the way. An underfilled tube will have an excess of sodium citrate, which will tie up some of the calcium the instrument is adding in, which will make it look like the blood's taking a very long time to clot. If you aren't on blood thinners, and you're not showing signs of a clotting disorder, you aren't likely to see the phlebotomist pull out a blue tube.

Light Green - Heparin

Heparin tube with gel separator - from bd.com

These were the most commonly used tubes in the chemistry section of the hospital lab. They're used for glucose (blood sugar) testing, electrolytes like sodium and potassium, and other important analytes like cholesterol, liver enzymes, and cardiac markers that can indicate a heart attack. This anticoagulant is usually a Lithium-Heparin salt, instead of a potassium or sodium salt, because most basic metabolic profiles (you'll sometimes hear them called a Chem-7 or Chem-some-other-number on TV medical shows) will measure potassium and sodium, and we don't want to falsely increase those numbers with our anticoagulant. We also can't use EDTA, because the calcium would look too low. 

Because chemistry testing is focused on the plasma, the blood is centrifuged to get the cells out of the way. Some tubes go an extra step with a built-in gel barrier, which keeps the cell portion trapped below so that even if you invert the tube, the cells stay put. This makes it easier to aliquot the sample (take small volumes from the main tube for other testing) without disturbing the cells and making it necessary to spin the tube again.

Gold - Gel Separator, No Additives

Gold tube, no additive - from bd.com

In situations where it's okay for the blood to be clotted, a gold top tube can be used. It has no anticoagulant, so after the blood has been in the tube for a few minutes, it will form a nearly solid clot. Once spun, the tube will have cells and serum separated by a gel barrier, which makes it easy to pour the serum off into other tubes for separate tests. These tubes are often used when the serum is to be sent to an outside lab for special testing (anything not done at the lab where it's drawn), because it's easier to pour the serum into transport tubes for refrigeration or freezing, and they're a little cheaper because they have no additives. 

Many labs use these as their workhorse tubes, accepting them instead of heparin tubes for chemistry workups. I don't actually know why the lab I was working in used the green tubes for most of the chemistry - a lot depends on the instruments being used in the lab and whether they have specifications for the test material. If your test's instructions say it needs to be a heparin tube, then that's what you should use, because the results may not be reliable if you use something else. Also, it's better for the patient if we can run several tests off of one tube, and not just to keep costs down. Repeated blood draws can lead to bruising, and if excessive, to phlebotomy-induced anemia. So, if you can choose to use either a green or a gold tube for a certain test, because both are allowed by the instrument's specifications, but another important test in the lab needs to be on a green top, it may make sense to bundle those tests together onto one tube.

Other - Special Cases

Some other colors are out there, but they're used infrequently and you're not likely to see them unless you're having fairly rare tests done. In our lab, dark blue tubes were used detection of heavy metals like copper or lead, because the tubes and interior of the caps were free of trace metals. Red top tubes had no additives, like the gold tubes, but contained no gel separator, so they could be used for some therapeutic drug levels - the gel has a tendency to absorb some drugs over time, so a red top would be more accurate in those cases. Gray tubes were used for lactic acid levels, but some places use them for glucose, because the potassium oxalate anticoagulant in the tubes stops the red cells from using it all up.

While different labs will use the same tubes for different tests, depending on their methodologies, a lavender top tube in one hospital will contain the same additives as one in any doctor's office. It's common sense, really - you don't want a part-time employee who works at two different facilities to get confused and use the wrong tube for a specimen collection, because it's what he's used to at the other job. Yes, it gets looked at in the lab, but we're all human and sometimes a wrong tube can go on an instrument, and since all the instrument does is read a bar code and perform the tests it's instructed to, you'll still get a result, and it may be very wrong. Consistency is key to medical and laboratory safety.