I recently mentioned that I have published a blog entry in a journal. The current entry is the reverse, where this blog entry is based on a recent publication (Krouwer, JS Interference Testing: Why Following Standards Is Not Always the Right Thing to Do. Journal of Diabetes Science and Technology, 2012;6:1182–1184.)
In this publication, I note that the CLSI standard about interference testing – EP7-A2 – recommends that a manufacturer may state that there was no interference if a substance meets a clinical goal where the level of bias from interference will not cause clinical harm. For example, if for substance “A” the clinical goal is bias from interference less than 10%, the manufacturer could state substance “A” does not interfere, even if it were true that substance “A” caused a bias of 9%.
This is wrong because it mixes the concept of finding an analytical interference (call this bias level 1) and the level of interference required to cause harm (call this bias level 2.) Laboratorians would like to know both concentration levels. So a table of interfering substances should look like this.
|A||200 mg/dL||Not detected||Yes|
Substances that fail would have more information.
The reason for this blog entry is that I just got a copy of CLSI C56-A, which is about interference testing for hemolysis, icterus, and lipemia and for this manufacturing dominated standards group, C56-A has the same problem as EP7-A2.