Elevated Cardiac Troponin in the Setting of Periodic Symptomatology: A Case Report

Abstract

Abstract Introduction/Objective Serial cardiac troponin measurement is a sensitive method to identify recent cardiac injury and is a necessary function of the clinical chemistry laboratory. We present a case of out-of-range cardiac troponin I (cTnI) elevation which remained spuriously elevated for at least 30 days. Methods Cardiac troponins were measured on a DxI (Beckman Coulter), Vitros 5600 (Ortho Clinical Diagnostics), iSTAT (Abbott), and Cobas e602 (Roche) according to the manufacturers’ instructions with appropriate controls. Heterophile antibody blocking (Scantibodies Laboratories) was performed according to the package insert. Results A 58-year-old male with a medical history significant for chronic non-ischemic cardiomyopathy with open valvular repair (ejection fraction 15-20%), chronic atrial fibrillation, and Hodgkin’s lymphoma in remission presented to a rural clinic with chest pain and a cTnI of 0.8 ng/mL (reference <0.04 ng/mL). He was transferred to our tertiary center for open revision. The patient’s cTnI (measured on a Beckman Coulter DxI) was above linearity threshold (>71.00 ng/mL) starting day 1 after surgery. The patient self-discharged against medical advice on day 16. On day 21 he experienced new chest pain and dyspnea and was readmitted with a cardiac troponin T (cTnT) of >35 ng/mL (iSTAT; reference <0.08 ng/mL) and cTnI again above threshold. This value remained elevated for the next five days despite abated symptoms. To address the discordant laboratory and physical findings, dilutional cTnI measurements on serum from day 30 demonstrated linearity. Heterophile antibody testing was negative. cTnI on the DxI machine remained >71.00 ng/mL but was separately measured as 3.4 ng/mL (Vitros 5600, reference <0.08 ng/mL). cTnT was found to be 1.05 ng/mL (Cobas e602; reference 0.00 ng/mL). Comparative examination of all methodologies was unrevealing. Conclusion This case demonstrates a spurious elevation of cardiac troponins which remarkably demonstrated linearity on serial dilution. Multiple testing methodologies were necessary to prove fallacy. The cause of the result remains unclear. The clinical pathologist should be aware of possible false positives and investigate unlikely continuous cardiac troponin elevations.