chem 7 vs chem10?

[tangent]

any big advantages to the extra 3 tests? - these seem to cost about the same...

more importantly, is there a neophites guide to interpreting the results and what all those numbers really mean?

thanks,

-t

[DrBaboon]

any big advantages to the extra 3 tests? - these seem to cost about the same...

more importantly, is there a neophites guide to interpreting the results and what all those numbers really mean?

Well, at least in the US, most of the older chemistry panels (chem-6, chem-24, chem-27, SMA-12, SMAC, or whatever) were abolished in the 1990's by the feds. The concern was that more and more tests were being included without having a reason before seeing the result. That in turn resulted in more frequent results that were unexpectedly abnormal, and resulted in a certain number of wild goose chases doing sometimes extensive (and expensive) additional testing of various sorts. Sometimes invasive or otherwise risky testing was pursued to "rule out" more significant abnormalities that were suggested by these unexpected abnormal results. Sometimes that resulted in "misadventures" that included adverse outcomes. Ergo, there actually were some good reasons to reformulate the panels.

For almost 10 years, we have have worked with the BMP (Basic Metabolic Panel) and the CMP (Comprehensive Metabolic Panel).

CPT Code 80048 Basic metabolic panel
This panel must include the following: Calcium (82310) Carbon dioxide (82374) Chloride (82435) Creatinine (82565) Glucose (82947) Potassium (84132) Sodium (84295) Urea Nitrogen (BUN) (84520)


CPT Code 80053 Comprehensive metabolic panel
This panel must include the following: Albumin (82040) Bilirubin, total (82247) Calcium (82310) Carbon dioxide (bicarbonate) (82374) Chloride (82435) Creatinine (82565) Glucose (82947) Phosphatase, alkaline (84075) Potassium (84132) Protein, total (84155) Sodium (84295) Transferase, alanine amino (ALT) (SGPT) (84460) Transferase, aspartate amino (AST) (SGOT) (84450) Urea Nitrogen (BUN) (84520)

If any of us are looking at older references, we'll see the use of older terminology and older panels.

And hopefully I've been sufficiently clear that what I've said is specific to the US, and is therefore probably not correct around the world (as far as terminology or composition of chemistry panels is concerned).

However, what I've said about how including more and more test in chemistry panels without have a reason up front to do so *is* correct regardless of where you are.

It comes down to Bayes' Theorem and Prior Probability. If you have a low prior probability, getting a positive test result does not mean the person has what you think they have - it's merely more likely to be a false positive.

Interpretting test results is more than looking at normal ranges to see if someone is "euboxic."

There are questions we each have to ask and answer about our reasons for the test (what we think about Prior Probability), and what we're going to do with the result. We also have to think in patterns.

IOW - you could have a list of possible reasons for the chloride to be elevated. But if you combine that with looking at a pattern that also contains the CO2 or other parameters, you end up with a different list.

It's like an Internal Medicine Board Exam question -- "if you're puking for 2 days and get dehydrated, but also have respiratory acidosis from COPD/CO2 retention, what does your BMP look like?" Of course, the boards would ask that in the reverse direction -- by giving you a BMP and asking you to match it to one of 5 patient profiles.

Unless someone finds a multichannel chemistry analyzer and is able to get it working AND be able to do QA & standardization on it, I don't think it's a high priority that trumps other items/services.

When I participated in some of the discussions last Fall on lab testing, I think I expressed my opinion that I would settle for a shorter, more simple menu, that I also thought was more sustainable.

I included glucose, BUN or creatinine, and potassium on my list of desired blood/serum/plasma chemistries. Toss in hemoglobin if you're not doing RBC counts by hemacytometer or a spun hematocrit. Glucose is already pretty ubiquitous in the form of home testing supplies. I gave a reference to Ames Azostix for BUN, and outlined a proposal for a wet lab test for BUN (which I wondered about performing at the same wavelength as hemoglobin testing via the Drabkin method).

It might not be optimal, but honestly, I wouldn't feel incapacitated by only being able to perform that abbreviated list of chemistries.

The gap is in finding a way to get potassium measured.

Ames used to sell the Seralyzer, which used a crown ether impregnated test strip for reflectance spectroscopy. That's long since obsolete. I don't know if Reflotron did one or not. They were not nearly as good as ion-selective electrodes or flame photometry (which is the traditional method). There is a reflectance photometer RQ Flex (http://morebeer.com/product.html?product_id=6249) that's used in soil chemistry and brewing/eonology that is sort of interesting, though there is information regarding interference from sodium. Of course sodium below a certain level is acceptable, but in blood serum or plasma, sodium is many times higher than potassium, so it's the opposite of what this reflectance photometer can handle.

Practically, I think a potassium selective electrode is probably the way to go.