Ischaemic heart disease

Beware of troponin false positive results: especially in COVID-19 cases

Regulators have reminded clinicians to be wary of false positive results with troponin testing, and the American College of Cardiology says this is a particular risk for patients with COVID-19.

In its latest Medical Devices Safety Update the TGA says caution is needed with high sensitivity troponin tests, for which there is a greater chance of false positive results and unnecessary treatment.

It notes that the TGA Incident Reporting and Investigation Scheme (IRIS) has received 289 reports of false positive troponin tests in the past nine years.

While this is a low incidence in the context of the large number of tests performed annually, health professional still need to be alert to the potential of false positive test results in conditions that may cause raised troponin levels.

“A positive troponin reading must be considered in light of other pathology results by laboratory staff prior to release of a report, and in combination with clinical signs and symptoms and electrocardiogram (ECG) results by medical staff, to prevent misdiagnosis,” it advises.

“Failure to detect a false positive troponin may result in the patient receiving unnecessary treatments, including invasive procedures.”

Meanwhile the American College of Cardiology has drawn attention to the abnormal elevation of troponin levels in patients with COVID-19 infection

The College draws attention to a recent article on the clinical course of patients with COVID-19, noting that detectable hs-cTnI was observed in most patients, and hs-cTnI was significantly elevated in more than half of the patients that died.

It is likely that direct (“non-coronary”) myocardial damage is almost the most common cause of elevated troponin levels in COVID-19, especially as the ACE2 receptor is also the binding site for the SARS-CoV-2 and it is present  in cardiomyocytes,

“Some have postulated that myocarditis might explain rise of hs-cTn in some cases, particularly as acute left ventricular failure has been described in some [COVID-19] cases. “

The advice is therefore that  elevated hs-cTn results are not sufficient to secure the diagnosis of acute MI, which should be based on clinical judgment, symptoms/signs, and ECG changes.

“Given the frequency and non-specific nature of abnormal troponin results among patients with COVID-19 infection, clinicians are advised to only measure troponin if the diagnosis of acute MI is being considered on clinical grounds and an abnormal troponin should not be considered evidence for an acute MI without corroborating evidence.

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