Characteristics of a 20-minute whole blood, assay for cardiac troponin T

Objectives: A qualitative whole blood rapid assay for cardiac troponin T (cTnT) was examined. The assay uses the same antibodies as for a benchmark ELISA, but the capture and detection roles were switched to enhance specificity. Design and Methods: The cTnT Rapid Assay(TM) and ELISA were compared in 643 samples from patients having myocardial infarction, coronary artery bypass surgery, ischemic heart disease, musculoskeletal disease, renal failure, or other noncardiac conditions. Concordance between the methods was compared using the McNemar Test and cTnT cutoff of 0.2 μg/L. Results: For the 'cutoff' of 0.2 μg/L, concordance between the cTnT Rapid Assay(TM) and ELISA was in the range of 90-95% for each group except the renal failure patients, where concordance was 77.9%. There was no significant difference between the cTnT Rapid Assay(TM) and ELISA, except in the renal failure and ischemic heart disease patients, where there was a greater number (p < 0.05) of cTnT Rapid Assay(TM) negative results when the ELISA was >0.2 μg/L. Overall concordance between the cTnT Rapid Assay(TM) and CK-MBmass was 78%. Conclusion: The McNemar test indicated that the cutoff for the cTnT Rapid Assay(TM) was 0.2 μg/L. Evidently the lower concordance among renal failure and ischemic heart disease patients reflects higher cTnT specificity for the Rapid Assay(TM) that was conferred by switching the capture and detection antibodies.