CARDIAC TROPONIN-I MEASUREMENT WITH THE ACCESS(R) IMMUNOASSAY SYSTEM - ANALYTICAL AND CLINICAL-PERFORMANCE CHARACTERISTICS

We evaluated the ACCESS(R) cardiac troponin I (cTnI) immunoassay as a marker for myocardial infarction (MI). Total imprecision was 6.0% to 1 3.5%, the minimum detectable concentration was 0.007 mu g/L, and the l imit of quantitation was 0.046 mu g/L. Comparison of cTnI measurement between the ACCESS and Stratus systems (n = 114) showed a proportional difference: ACCESS cTnI = 0.0996 Stratus cTnI + 0.049 mu g/L (r = 0.8 11). Fifty-nine of 61 ambulatory patients without cardiac symptoms had no detectable cTnI (95% range, 0.00 to 0.025 mu g/L). The optimum cut off for discriminating MI (n = 289, 45 with MI) was 0.15 mu g/L by rec eiver operator characteristic curve analysis; at this cutoff, the ACCE SS cTnI assay showed a sensitivity of 88.9% (95% CI, 79.7-98.1%) and s pecificity of 91.8% (95% CI, 88.4-95.2%). The ACCESS cTnI assay result s showed 89.4% and 93.0% concordance with the MB isoenzyme of creatine kinase (CK-MB) mass and Stratus cTnI results, respectively, for class ification of patients with suspected MI. The ACCESS cTnI assay appears to show sensitivity and specificity comparable with those of both CK- MB mass and Stratus cTnI assays for the diagnosis of MI in patients pr esenting within 12 h of onset of symptoms.