CLSI EP11 – Uniformity of claims – update


The CLSI document EP11 was originally published in 1995 as a proposed document. The document explains among other things how the same performance data can lead to different manufacturer’s claims. EP11 provides a terminology for claims so that users (labs) can understand the meaning of claims.

Even though EP11 was approved by its subcommittee and the area committee, the Board of Directors cancelled the project in 2003. Although supported by most manufacturers, there were a few who strongly opposed it and influenced the Board. It does not appear in the CLSI catalog. With new CLSI policy the area committee has the final say on documents, so I brought up revisiting EP11 at a recent CLSI meeting.

The feedback was virtually no support to bring back EP11 so it is a dead issue. One of the main comments was to let each EP document manage its own way of stating performance claims. I pointed out that the current way claims are stated is often poor. As one example in EP7-A2 (about interferences) it is stated:

“The following substances, when tested in serum at AST activities of 25 and 200 U/L according to the CLSI protocol, were found not to interfere at the concentrations indicated. A bias of less than 10% is not considered a significant interference.”…

This seems pretty bogus to me. It’s just bad science to say “found not to interfere”, if a substance does interfere (even if the bias is considered not to be significant). Moreover, since many of these documents have gone through several revisions and have not improved the way claims are stated, it seems like a brush off to say leave claims to each EP document.

But, perhaps there’s another way of looking at things. A few years ago, I proposed a method for a lab to compare the quality among its assays by calculating Cpm (process capability – a unitless measure) for all assays using existing quality control data (1). But one requirement for this to work is for each lab to have performance goals for each assay. When I asked a few lab directors what their performance goals were, I got back blank stares, followed eventually with, do you mean CLIA goals? Hence it would seem that most lab directors do not think in terms of performance goals and this may be more important than how performance claims are stated.


  1. Assay Development and Evaluation: A Manufacturer’s Perspective. Jan S. Krouwer, AACC Press, Washington DC, 2002 pp96-101.

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