CARDIAC TROPONIN-T IMMUNOASSAY FOR DIAGNOSIS OF ACUTE MYOCARDIAL-INFARCTION

We evaluated the analytical and clinical performance of an immunoassay for cardiac troponin T (cTnT). Within-run and total imprecision range d from 1.6 to 11.3%. The sensitivity and linear range was 0.015 and 13 mu g/L, respectively. Frozen samples were stable for at least 8 weeks . No interferences were seen with lipids or bi[irubin (total and conju gated). Hemoglobin caused a negative bias at concentrations >4 g/L. He parinized plasma showed a 6% negative bias compared with serum. The cl inical utility of cTnT was compared with that of creatine kinase (CK)- MB (mass assay). The sensitivity of cTnT measurements from 63 patients with acute myocardial infarction (AMI) (cTnT cutoff 0.1 mu g/L) was 6 0% at 0-3 h, 59% at 3-6 h, 94% at 6-9 h, 90% at 9-12 h, 99% at 12-24 h , 92% at 24-48 h, 83% at 48-72 h, and 100% at 72-96 h. Corresponding r esults for CK-MB (cutoff 5.0 mu g/L and 2.5% relative index) were 45%, 64%, 82%, 97%, 87%, 81%, 54%, and 59%. The specificity of the markers from 49 non-AMI patients was 46% and 79% for cTnT and CK-MB, respecti vely. We show that CK-MB is more specific for diagnosis of AMI, and pr opose that cTnT is more sensitive to myocardial injury.