Assay specifications are not based on clinical needs

Published specifications for assays are often said to be based on clinical requirements – an example is the glucose meter specification ISO 15197:

“The minimum acceptable accuracy criteria are based on the medical requirements for glucose monitoring.” 

This blog entry shows that rather than medical requirements, specifications are based on currently achievable performance.

Regulators have to make a binary decision – to approve or reject an assay. The issue can be seen in the following table

  Benefit Risk
Approve assay Information helps clinicians Assay errors cause wrong
medical decisions
Reject assay No wrong medical decisions
from assay errors
Lack of information from assay causes harm

Consider glucose meters. Each year, a certain percentage of people (albeit very low) are harmed by glucose meter errors. If one were to use more stringent specifications that all existing glucose meters would fail to meet and would have to be taken off the market, the harm from the lack of information from the meters would be much greater than the harm caused by existing glucose meter errors. If the existing glucose meter error rate increased, the analysis would be the same – the lack of information from the meters would be much greater than the harm caused by existing glucose meter errors.

Given that current glucose meters have a certain performance (bias, imprecision, ease of use, and so on) a new meter is expected to have comparable performance to the performance of current meters and specifications take into account current performance. This has nothing to do with the clinical need for glucose meter performance.

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