Unnecessary coronary angiography due to false positive troponin I results in a 51-year-old man

Role of Antitroponin Antibodies and Macrotroponin in the Clinical Interpretation of Cardiac Troponin

Cardiac troponin is extensively used as a biomarker in modern medicine due to its diagnostic capability for myocardial injury, as well as its predictive and prognostic value for cardiac diseases. However, heterophile antibodies, antitroponin antibodies, and macrotroponin complexes can be observed both in seemingly healthy individuals and patients with cardiac diseases, potentially leading to false positive or disproportionate elevation of cTn (cardiac troponin) assay results and introducing discrepancies in clinical interpretations with impact on medical management. In this review article, we describe the possible mechanisms of cTn release and the sources of variations in the assessment of circulating cTn levels. We also explore the pathophysiological mechanisms underlying antitroponin antibody development and discuss the influence exerted by macrotroponin complexes on the results of immunoassays. Additionally, we explore approaches to detect these complexes by presenting various clinical scenarios encountered in routine clinical practice. Finally, unsolved questions about the development, prevalence, and clinical significance of cardiac autoantibodies are discussed.

Antibody-mediated interferences affecting cardiac troponin assays: recommendations from the IFCC Committee on Clinical Applications of Cardiac Biomarkers

The International Federation of Clinical Chemistry Committee on Clinical Applications of Cardiac Biomarkers (IFCC C-CB) provides educational documents to facilitate the interpretation and use of cardiac biomarkers in clinical laboratories and practice. Our aim is to improve the understanding of certain key analytical and clinical aspects of cardiac biomarkers and how these may interplay. Measurements of cardiac troponin (cTn) have a prominent place in the clinical work-up of patients with suspected acute coronary syndrome. It is therefore important that clinical laboratories know how to recognize and assess analytical issues. Two emerging analytical issues resulting in falsely high cTn concentrations, often several fold higher than the upper reference limit (URL), are antibody-mediated assay interference due to long-lived cTn-antibody complexes, called macrotroponin, and crosslinking antibodies that are frequently referred to as heterophilic antibodies. We provide an overview of antibody-mediated cTn assay interference and provide recommendations on how to confirm the interference and interpret the results.

On the Effect of Heterophilic Antibodies on Serum Levels of Cardiac Troponins: A Brief Descriptive Review

Serum levels of cardiac troponins can be increased both with myocardial damage and in the absence of myocardial damage. In the second case, this is due to the influence of false-positive factors, among which heterophilic antibodies play a significant role. Understanding the causes of the formation of heterophilic antibodies, the features and mechanisms of their effect on serum levels of cardiac troponins, is an important condition for interpreting a false-positive result due to the influence of heterophilic antibodies. This brief, descriptive review presents the causes of heterophilic-antibodies formation and discusses their effect on serum levels of cardiac troponins.

A non-ischaemic cause of elevated troponin

A 27-year-old woman with chest pain was admitted for elevated troponin levels. Troponin remained mildly elevated upon repeat testing, and a review of the medical record revealed that she had had an elevated troponin level in the past. She had a cardiac catheterisation that revealed angiographically normal coronary arteries. Repeat troponin testing with and without ethylene glycol revealed a negative troponin level after addition of ethylene glycol, suggesting antibodies were interfering with the assay.

Interference from heterophilic antibodies in troponin testing. Case report and systematic review of the literature

Heterophilic antibodies, comprising both "true" heterophilic antibodies and human anti-mouse antibodies (HAMA), represent an important source of interference in laboratory medicine, thus including cardiospecific troponin(s) testing. We describe the case of a 76-years-old woman with implausible and persistent elevation of cardiospecific troponin I, which was finally attributed to interference from heterophilic antibodies. According to literature data, the frequency of this interference ranges between 0.1 and 3.1%, is almost unpredictable and unsuspected, may involve both cardiospecific troponins I and T, and may virtually affect any type of immunoassay, either one- or two-step. The presence of interfering antibodies should always be suspected when test results do not go hand in hand with the clinics, or with the results of additional radiological and laboratory investigations. Once other causes of interference have been ruled out, test repetition with an alternative assay and removal of interfering antibodies with heterophilic antibodies blocking reagent, normal mouse serum, immobilized protein A column or polyethylene glycol may be advisable. As a simple alternative, measurement of serial dilutions of suspected samples usually shows nonlinearity of test results in the presence of heterophilic antibodies.

Fluctuation of spuriously elevated troponin I: a case report

Serum troponin is a useful laboratory study for the diagnosis of acute myocardial infarction. However, elevations can also be seen in a variety of other diseases processes. Falsely positive troponin values caused by interference with current troponin assays have been reported. We report a unique case that demonstrates the fluctuation of falsely elevated troponin correlating with hemoglobin, serving as a marker of heterophile antibody levels. A 74-year-old gentleman presented to our Emergency Department with a several-day history of increasing shortness of breath associated with a new-onset chest pain and a troponin I level of 77.28 ng/mL. Throughout his stay, fluctuations in measured troponin levels correlated strongly with fluctuations in hemoglobin levels. Several investigations confirmed false elevated troponin levels secondary to heterophile antibody interference. We conclude that hemoglobin trending in our patient represented a surrogate measure of his heterophile antibody titers with time and that fluctuations in these levels correlated with respective fluctuations in the falsely elevated troponin levels.