Research Courtesy of HyTest, Ltd.
The presence of cardiac troponin I autoantibodies in blood has been known for a long time. These autoantibodies bind to the stable part of cTnI and may be found in the blood of both healthy people and people with different diseases. They may interfere with the cTnI tests if the areas of the cTnI molecule that the assay antibodies should recognize are covered by autoantibodies. This can result in underestimation of cTnI concentration in blood samples.
In this article, HyTest’s researchers investigated in more detail the epitope specificity of troponin autoantibodies that prevent an efficient detection of cTnI by such mAbs that bind to epitopes commonly utilized in commercial assays. This study shows that the autoantibodies investigated are specific to the conformational epitopes found in the troponin I-T-C ternary complex but not in the binary I-C complex or free cTnI. Only when as part of the ternary complex, the detection of cTnI was compromised in the presence of autoantibodies. On the other hand, based on the data the ternary I-T-C complex is one of the main cTnI forms only in the early samples of acute myocardial infarction patients. This means that if the blood of an AMI patient contains autoantibodies the risk of obtaining falsely low troponin levels is higher in samples taken shortly after the onset of the AMI.
Vylegzhanina AV, et al. Anti-Cardiac Troponin Autoantibodies Are Specific to the Conformational Epitopes Formed by Cardiac Troponin I and Troponin T in the Ternary Troponin Complex. Clin Chem. DOI: 10.1373/clinchem.2016.261602 Published December 2016
Autoantibodies were discussed also in the editorial of the same issue of Clinical Chemistry:
Park JY and Jaffe AS. Troponin Autoantibodies: From Assay Interferent to Mediator of Cardiotoxicity. Clin Chem. DOI: 10.1373/clinchem.2016.268920 Published December 2016