A false-positive troponin assay leading to the misdiagnosis of myopericarditis

Figure 1:. Cardiac investigations of a 16-year-old girl with a misdiagnosis of myopericarditis. (A) Normal electrocardiogram from the patient’s initial presentation to the emergency department. (B) Cardiac troponin I levels and anti-inflammatory treatments from initial presentation to 80 days after presentation. Light grey and dark grey bars represent duration of anti-inflammatory treatment with naproxen and prednisone, respectively. (C) Transthoracic echocardiogram from 30 days after the patient’s initial presentation, at time of the maximum level of cardiac troponin I, showing normal global longitudinal strain.

Figure 2:. (A) Mechanisms for in vivo and in vitro analytic interference with troponin assays. The presence of a macrotroponin, a high–molecular-weight complex of immunoglobulin and troponin, can lead to false-positive results owing to its slower clearance from circulation. The presence of heterophilic antibodies or autoantibodies can lead to false-positive results by bridging the assay’s capture and detection antibodies, generating a false signal. (B) Polyethylene glycol (PEG) precipitation test to assess possibility of circulating macrotroponin. The addition of PEG leads to the precipitation of high–molecular-weight molecules, including macrotroponin. After incubation with PEG and centrifugation, the supernatant, now cleared from macrotroponin, is measured and the recovery rate can be calculated (supernatant troponin concentration, corrected for the volume of PEG, divided by the initial troponin result). A low recovery rate suggests the presence of macrotroponin.