CLSI EP21-A2 (Total Error) – rejected after 5 years

Reminds me of the Bluto clip “Seven years of college down the drain” So what happened?

A previous president of AACC explained his reject vote of EP21 …

“Pre-and post analytic error is not measurable in a reproducible manner. It will vary by location (ED vs. clinic, ICU private office etc.), personnel obtaining samples, reporting results.  It will vary depending on the LIS/interface of the institution, distance from the lab that the blood is drawn and then transported to, etc. The lab and manufacturers have very little control over this.  Bias and imprecision can be measured quite well and then total analytic error can be estimated.”

This person either doesn’t understand EP21 or pretends not to understand EP21.

EP21 does not attempt to assess error sources.
EP21 does not combine error sources such as implied in the last sentence of the commentator.
EP21 simply measures differences from the comparative assay as total error.

Pre-analytical error is part of what is measured in an EP21 experiment in certain cases. Some examples:

Air bubbles allowed in a syringe of arterial blood contaminate the pO2 measurement with room air.
A tacrolimus assay involves a manual pretreatment step that if performed incorrectly can affect results.

Moreover, EP21 is an experiment. No results are reported to clinicians. Patient acquisition, use of the LIS, and reporting of results will not be conducted according to the routine methods of the laboratory. So any errors that are part of the experiment and not representative of routine use should be excluded. Also, many pre-analytical errors that are important in routine use will be nullified by the fact that this is an experiment. Example: pre-analytical error of sample preparation is likely to be nullified if the experiment is a split sample design.

So why mention pre-analytical error at all?

Because there is the opportunity to introduce bias in the experiment by eliminating the opportunity for pre-analytical error to occur.

Example: compare split sample venous blood instead of a finger stick sample to venous blood for assays that routinely use finger stick and whose comparative assays use venous blood. This would be biased because one has excluded the possibility for error to occur from a finger stick.

So the commentator’s argument against mentioning pre-analytical error doesn’t seem like a valid reason to reject the document.


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