Characteristics of a 20-minute whole blood rapid 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™ and ELISA were compared in 643 samples from patients having myocardial infarction, coronary artery bypass surgery, ischemic heart disease, musculo-skeletal 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™ 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™ 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™ negative results when the ELISA was >0.2 μg/L. Overall concordance between the cTnT Rapid Assay™ and CK-MBmass was 78%. Conclusion: The McNemar test indicated that the cutoff for the cTnt Rapid Assay™ 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™ that was conferred by switching the capture and detection antibodies