Cardiac troponin assay considerations

Due to assay difficulties there were early concerns of the specificity of cardiac Troponin T in patients with renal failure, and also concerns that there was cross-reactivity with injured skeletal muscle. These problems do not occur with second and third generation assays for cardiac toponin T.

There are also multiple assays available for cardiac troponin I - which require standardisation. Assays for troponin I may also have problems due to interference by fibrin, heparin, heterophile antibodies and human anti-mouse antibodies. The latter may be a problem in those that either make antibodies or receive therapy with extrinsic antibodies.

For most clinical tests, the 97.5 percentile is used as a cut off for normality, but an editorial in Circulation (Sept 2000) suggested that for cardiac troponin T, cardiac troponin I and CK-MB the 99th percentile should be regarded as the upper limit.

Reference:

• Jaffe A.S. et al. Editorial. It's Time for a Change to a Troponin Standard. Circulation. Sept 2000;102(11):1216.
• Lindahl B. et al. Markers of myocardial damage and inflammation inrelation to long-term mortality in unstable coronary artery disease. NEJM 2000;343(16):1139-1147