Any Phlebotomists Around?

Hello, phlebotomist here! They need to be centrifuged for 10 minutes to seperate the serum. Once this is done, they can be tested. We don't use microscopes anymore - most labs have machines which can perform a variety of tests.

Creatinine and eGFR fall under a set of tests called "Urea and Electrolytes", which measures kidney function and also includes sodium, potassium and urea levels. Usually the eGFR has to be ordered as an additional test, but if there are any abnormal results in the initial U&E the lab will do it anyway. The BUN is seperate but can usually be performed on the same machine.

It would take roughly two hours for these tests to be processed in the average lab.

Also, the type of tests performed would vary depending on the suspected cause. We don't perform BUN very often in the lab I work at (I work in the UK, so it might be different elsewhere) If we suspect renal failure, we'll also do a urinalysis to look for white blood cells and protein. Some doctors will order a phosphate test.

Phosphate can be determined through a standard blood test. As for urinalysis - the most basic tests are performed through a microscope, and these would normally be looking for

red blood cells (presence of which may indicate inflammation, injury or kidney disease)

white blood cells (high levels of which may indicate infection or inflammation in the urinary tract)

epithelial cells (it's normal to find a low level of epithelial cells from the bladder. It's less normal to find them from the kidneys. Infection, inflammation and malignant growths increase the number of cells. The location of these cells can tell us a lot about what's going wrong - so for example, if there's a bladder infection, there'll be an increase in the type of cells found there)

Bacteria (fairly self explanatory!)

Casts (this link explains casts pretty well)

We also do a 'dipstick' test, which is basically a strip of specially prepared paper. They are coated in chemicals which react with the urine. We most commonly use these to test for glucose, protein, urine PH, blood, bilirubin and nitrate.

This site is a superb resource if you're interested in laboratory testing. We actually use it at work occasionally if we get a test we've never seen before.

You're welcome! Always happy to help. A CBC wouldn't need to be centrifuged although they do usually need to be shaken a little before testing in case of clots. As a rule, most liver/thyroid/kidney function tests will need centrifuging.

Quentin Nokov said:

A character of mine is having a BUN, Creatinine, and GFR blood test done to see if his kidneys are failing, my question is, would all three of these tests have to be processed before analyzed? If so, how long would they have to be in the centrifuge for, and if not, how is it analyzed. By a machine or under a microscope?

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GFR is a calculation based on serum creatinine ... so he has BUN and Creatinine done, then GFR calculated. It's based on weight, age, sex and stuff.

http://www.kidneyfund.org/kidney-health/kidney-basics/kidney-test-egfr.html

How fast do you need it?

1. Draw the blood in a "red top" vacuum tube (no anticoagulants in it)
2. Let it clot - usually by the time the phlebotomist is back to the lab it's clotted
3. Centrifuge X minutes (depends on what model centrifuge)
4. Separate serum(the clear stuff) from the red cells with a filter pusher (shove it into the tube
5. Put some serum into a machine's sample cup
6. Run test ... time taken depends on how many tests, if controls are in control, etc. and how many different machines it takes. Some labe run the BUN and Creatinine in the same machine, others have them split.
7. If test is grossly abnormal, it is repeated unless patient is a known kidney patient

The tube-top colour used will vary depending on where you're setting the story (we use gold tops for these tests) The machines we use don't require physical separation of serum. After centrifuging, there's a gel layer between the blood and serum, and our machine takes the serum directly from the tube. Of course, this will vary from lab to lab.

Tsu Dho Nimh's point about the repeated test is quite important - unless the patient has a known history of deranged test results, the lab will typically run the bloods again.

And you're very welcome

Derpduhderp. I saw this thread and thought "they still do that?!"

Of course, they do! It's PHELBOTOMY, not phrenology. My sister's a phlebotomist, so I should have a better idea of what's going on here.

Derpduhderp.