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Analytical Issues Surrounding Troponin Assays



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Analytic Confusion: Sensitivity and Imprecision of cTn Assays

Slide 9

October 2010

Based on evidence that even small amounts of the cardiac specific troponin reflect incremental risk and indicate myocardial injury, consensus documents recommend that the normal range of troponin be set at the 99th percentile of a normal healthy population. Furthermore, the recommendations from the IFCC working group on standardization of cardiac markers state the total imprecision should be < 10% at the 99th percentile. The logic being that failure of this goal could increase the risk of reporting misleading results that may prompt unnecessary confirmatory testing or lead to clinical inaction when inappropriately low concentrations are reported.

Because of this recommendation, manufacturers must now provide this information on the package insert and it has become clear that commercial troponin assays are unable to achieve this acceptable precision. The precision also varies by specimen type and platform within the same manufacturer, as the larger instruments generally have better analytical characteristics. Most healthy normal individuals are then below the limit of quantitation and the lack of precision limits the ability to detect and define significant elevations in troponin at the low end of the range.

This table shows the precision characteristics of the assay used here at Mayo, the 4th generation Roche troponin T assay. You can see the 10% coefficient of variation is slightly greater than the 99th percentile concentration.

Analytic Confusion

 


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