Analytic and clinical evaluation of the Abbott AxSYM cardiac troponin I assay

We evaluated the AxSYM immunoassay for the quantification of cardiac tropon in I (cTnI). Total assay imprecision, expressed as coefficient of variation ,, ranged between 5.6% and 8.3% for commercial control serum samples and be tween 4.2% and 13.9% for pooled patient samples. Linearity was verified up to 42 mu g/L. Triglycerides (up to 1,000 mg/dL) did not interfere with the assay, but minor hemolysis and clinically relevant hyperbilirubinemia cause d a negative bias. In 186 patient samples, AxSYM cTnl levels correlated sig nificantly with data obtained with the Stratus II cTnI fluorometric enzyme immunoassay but were 3 to 4 times higher on AxSYM than on Stratus II. In II I healthy blood donors, the reference range for cTnl levels on AxSYM was 0. 0 to 04 mu g/L. After eccentric isokinetic exercise, healthy volunteers sho wed a rise in creatine kinase MB mass (AxSYM) but not in cTnl. On AxSYM and Stratus II, cTnl levels increased above the manufacturer's cutoff for acut e myocardial infarction in all 17 patients followed up after onset of infar ction-related chest pain but in only I of 91 control subjects. The AxSYM cT nl assay is a valid alternative for the detection of myocardial injury with diagnostic performance comparable to the established Stratus cTnl assay.