Can Troponin T replace CK MBmass as “gold standard” for Acute Myocardial Infarction (“AMI”)?

Abstract

Diagnosis of definite “Acute Myocardial Infarction” by the old WHO criteria depends on the diagnostic sensitivity and specificity of the biochemical marker used. Troponins have higher diagnostic sensitivity and specificity than the current “gold standard” for AMI, CK MBmass. Troponin T (TnT) provides both diagnostic and prognostic information on Minor Myocardial Damage (MMD) even in patients without increases of CK MBmass. Consequently, we evaluated the possibility of replacing CK MBmass with TnT. We first re-evaluated a previous, well-documented material of 502 time series from AMI-suspected cases, 50 % of which were primarily classified as AMI by CK MBmass ≥10 μg/L. We found that a TnT discriminator limit of 0.40 μg/L gave the same AMI prevalence. We then identified from our laboratory data base 1995 - 1998 acute patient episodes with ≥ 3 pairs of CK MBmass and TnT. This resulted in 754 episodes with max CK MBmass ≥ 10 μg/L (AMI), 93 episodes with maximal CK MBmass < 10 μg/L and TnT ≥ 0.10 μg/L (MMD), and 730 episodes with max concentrations below the discriminators of both markers (NOT-MMD). TnT ≥ 0.40 μg/L detected 91 % of all AMI giving a posterior probability of “AMI” > 99 %. The criterion: “maximal TnT within the interval 0.10 - 0.40 μg/L” detected 94 % of all MMD and 9 % of all AMI giving posterior probabilities about half MMD and half “small AMI”, the latter characterized by less than 3-fold increased maximal CK MBmass. Thus, this TnT interval confirmed the gradual transition between MMD and small AMI. We suggest gradation of myocardial damage by TnT.