Revealing false or true positivity of high-sensitivity troponin

Revealing false or true positivity of high-sensitivity troponin

In October 2014, BMJ - Education in Heart published a study entitled "Analytically false or true positive elevations of high sensitivity cardiac troponin: a systematic approach". The study summarizes a systematic approach to the management of patients with suspected false-positive cardiac troponin results based on real-life cases. The in-depth reading of this paper can help to find the causes of elevated troponin, summarize the causes of false-positive results, and better determine the true-positive and false-positive results, so as to provide more patients with a more scientific basis for testing.

Cardiac troponin is a protein molecule that regulates contraction of rhabdomyosin, is involved in calcium-mediated muscle contraction, and is a structural protein of skeletal and cardiac muscle. It consists of three subunits, troponin C (TnC), troponin T (TnT), and troponin I (TnI).The cardiac isoforms of TnT and TnI (cTnT and cTnI) have different amino acid sequences and unique antigenic epitopes from the corresponding isoforms in skeletal muscle, resulting in a high degree of cardiac specificity.

Case Study:

A 53-year-old female patient with elevated cardiac troponin T (hs-TnT) values was admitted to the hospital. There was no prior history of cardiac disease, but she presented with dyspnea and weight loss during light exercise. After a variety of tests, including cardiac ultrasonography, coronary angiography, and cardiac magnetic resonance imaging, the results were normal, but the concentration of hs-TnT was very high. To confirm the diagnosis, repeat measurements of hs-TnT were made and other laboratory tests were performed. In addition to the elevated hs-TnT, high titre antinuclear antibodies and mild elevations of other autoimmune disease markers were also found. Cardiac magnetic resonance imaging showed enhancement around the heart (Figure 1), consistent with acute pericarditis. Myocardial biopsy findings (Figure 2) showed the presence of signs of inflammatory cardiomyopathy.

Revealing false or true positivity of high-sensitivity troponin

The final diagnosis was systemic sclerosis with pulmonary and cardiac involvement. The patient was treated with corticosteroids, which resulted in a decrease in troponin values and relief of dyspnea, but also symptoms of sclerosis of the skin.
This case emphasizes the important relationship between the clinical and laboratory settings and the need for further evaluation of abnormal laboratory results. It also reminds physicians to consider a variety of factors in the diagnostic and therapeutic process to avoid misdiagnosis and unnecessary treatment.

Lum et al. have summarized several causes of false positive troponin (Box 2)

Revealing false or true positivity of high-sensitivity troponin

Increased sensitivity allows earlier and faster detection of non-ST-segment elevation myocardial infarction (NSTEMI), but also detects hitherto unsuspected cardiac pathology in the absence of ischemic heart disease. This increased sensitivity poses a challenge to most modern diagnostic methods and has prompted the need for more sensitive and specific imaging techniques, including cardiac magnetic resonance imaging (cMRI) and coronary CT angiography. As these technologies may not be readily available in most hospitals, mislabeling of "true positives" as "false positives" may occur. Prof. Evangelos Giannitsis' team recommends the use of simple algorithms when laboratory results do not match clinical results and analytical errors are suspected (Box 3).

Revealing false or true positivity of high-sensitivity troponin

Direct communication between clinicians and laboratory departments will facilitate timely interdisciplinary evaluations and help prevent unnecessary and potentially harmful diagnostic and therapeutic procedures.

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