A clinical and laboratory approach used to elucidate discordant results of high-sensitivity troponin T and troponin I

Abstract

BackgroundCareful interpretation of discordant results in high-sensitivity troponin measurements is necessary in cases of suspect immunoassay interferences. We describe several procedures taken in a case of a polymorbid patient with chest pain, without clear evidence of myocardial necrosis and with increased high-sensitivity cardiac troponin T (hs-cTnT). We checked the Vafaie's algorithm for the evaluation of suspect interference in troponin measurements. MethodsWe conducted a case report analysis, additional measurements, a dilution test and pretreatment of plasma with blocking agents. ResultsConcentration of hs-cTnT (99th percentile of “healthy” population 14ng/L) increased from 120.1ng/L to 280.4ng/L during an 8-month period and decreased to 216.3ng/L during the following month with repeatedly negative troponin I (TnI), hs-cTnI, myoglobin and creatine kinase MB (CK-MB). Suspected false positivity of hs-cTnT was further confirmed by treatment of plasma with an antiheterophile blocking agent (hs-cTnT before treatment 280.4ng/L, after 16.53/16.23ng/L). This outcome was further confirmed by the manufacturer's experiments. ConclusionsThe false-positive results of hs-cTnT were caused by the presence of extremely rare high molecular weight protein, presumably IgM, most likely HAMA (human anti-mouse antibody). Only the pre-treatment of plasma with a blocking agent provided a reliable indication of the interference. Cooperation among clinicians, laboratory personnel and the manufacturer is essential.