"Troponinosis", the Cardiologist's Curse-When Clinic-Laboratory Interaction Unveils the Mystery: A Case Report

Abstract

Cardiac troponins are key diagnostic and prognostic biomarkers in acute myocardial infarction and, more generally, for the detection of myocardial injury. Since the introduction of the first immunochemistry methods, there has been a remarkable evolution in analytical performance, especially concerning a progressive improvement in sensitivity. However, the measurement of circulating troponins remains rarely susceptible to analytical interferences. We report a case of persistently elevated troponin I concentrations in a patient with known ischemic heart disease, which almost led to unnecessary diagnostic-therapeutic interventions. A prompt laboratory consultation by the cardiologist ultimately led to the identification of an analytical interference due to troponin macrocomplexes (macrotroponin) causing elevated troponin values in the absence of a clinical presentation compatible with myocardial damage.

Keywords: acute coronary syndrome; analytic interference; high-sensitivity troponin; immunoglobulin; laboratory tests.

Figure 1

Panel (A): ECG diagnostic for inferior STEMI; Panel (B): the diagnostic coronary angiography; Panel (C): the final result after PTCA.

Figure 2

Panel (A): EKG showing diffuse ST-segment elevation; panel (B): evidence of no occlusion of the vessel and good result of previous PTCA.

Figure 3

Possible biochemical mechanisms of false-positive interferences in troponin assays: 1—Heterophile antibodies may cause false-positive results by acting as a bridge between capture and detection antibodies in the absence of cTn. Macrocomplexes (macro-cTn) reduce the plasma clearance of cTn, causing an increase in the circulating concentrations of complexed molecules that are eventually measured with the immunoassay. 2—PEG treatment induces the precipitation of macrocomplexes, leaving the uncomplexed cTn molecules in the supernatant after centrifugation of the sample.