Saturday, February 24, 2007

Is it a Job or a Game?

This is my weekend to work (or at least to go to the lab and blog while I get paid). We're on minimum staffing on the weekends, which is mostly fine since we're on minimum workload most weekends.

So I took this opportunity to work on my CAP survey in Blood Bank. CAP, which stands for the College of American Pathologists, require every tech to do proficiency testing in each department they work in a couple of times a year in order to maintain their certification. Since I'm a generalist, I do two CAP surveys a year in each of: blood bank, hematology, coagulation, chemistry, body fluids, and urinalysis. Some of the surveys are as simple as doing QC (quality control) on an analyzer and then running the specimen like a patient specimen, but the blood bank surveys are usually a little trickier.

Today's survey was a blood type and Rh, an antibody screen, and a DAT. The DAT (direct antiglobulin test) is a test for early exposure to an antibody, while it's still bound to the patient's red cells on their antigenic sites. Later, the antibody is found circulating in the plasma, but it takes a few weeks for the immune system to start producing it's own antibodies after exposure. Once the antibody is in the plasma, by the way, it's found with an antibody screen, and then an antibody ID panel, which is also called an indirect antiglobulin test. all that? The reason it's pertinent is that blood banking is fun. It's like a puzzle game. You start with a tube of whole blood in EDTA anticoagulent. You spin it down to seperate the red cells from the plasma, and then you start picking the puzzle apart. Is it positive for an unexpected antibody? Is it an autoantibody (generated by the patient's own an allergy) or an alloantibody (generated in response to exposure from a previous transfusion or other outside source)? If it's an autoantibody, is it masking an underlying alloantibody? Is there one antibody, or more than one? What can be ruled out conclusively? What can be ruled in definitively?

It's like a sudoku puzzle or a crossword puzzle. You look at the evidence, form a hypothesis, and start testing that hypothesis. If it turns out to be start again.

It's particularly fun when there's time to play around with it in your head. Not while the patient is bleeding to death in the ER, for instance. When it's a survey, and you know there will be a puzzle designed into it (because it's a proficiency test), and nobody's life depends on it being done speedy-quicko.

So my imaginary survey patient today turned out to be a B pos patient with a DAT that's positive for IgG antibody on the red cells, but not for complement.

And now I'm feeling that free feeling you get when you have Monday's homework done on Friday night, because I won't have to do another blood bank survey until summer. :-)

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