Cardiac troponin I should replace CKMB for the diagnosis of acute myocardial infarction.

Cardiac troponin I (cTnI) has been reported to be a highly specific marker for cardiac injury. We investigated the performance of this assay in patients admitted to a coronary care unit for suspected acute myocardial infarction (AMI), patients with extensive skeletal muscle damage, marathon runners and as a routine diagnostic test over a four week period. cTnI proved to be as sensitive a marker for AMI as creatine kinase/MB isoenzyme (CKMB) in patients admitted to the coronary care unit. In 10 patients with a proven AMI, the cTnI remained elevated from 69 to 183 h with a median time of 127 h. Cardiac troponin I had superior specificity to CKMB in patients with skeletal muscle damage. It was very useful in these patients to confirm or exclude concurrent myocardial damage. In routine diagnostic use, cTnI had greater efficiency than CKMB to classify patients as having an AMI. Consequently cTnI should replace CKMB as a marker for AMI.