What Do You Think is Causing This False Positive Troponin Measurement?
A 60-year-old male presented with vague chest discomfort that had been intermittent for three days, with the last episode starting three hours prior to the ED visit. The symptoms were described as pin-prick, lasting <1 min, and not associate with exertion, radiation, SOB, diaphoresis or N/V.
He reported being in good heath, and was able to swim for 30 minutes, five days a week.
Past Medical History:
- Rheumatoid arthritis, affecting his knees and hands.
- No prior significant cardiac history; specifically, no MI or revascularization. Increased cholesterol controlled with diet.
- PRN Nonsteroidal use for joint pain
BP 95/60 mmHg. Heart rate 65 BPM. Respiratory rate 22. afebrile
HEENT: (-) JVD
Cardiac: regular rate and rhythm. No murmurs, gallops
Abdomen: mildly obese, bowel sounds present, non-tender, non-distended Peripheral pulses: 2+ without bruits
Extremities: no edema; mild hand and knee tenderness to palpation
BUN/creatinine: 25/1.0 mg/dl
hemoglobin: 14.8 gm/L
ABG on room air: pO2 120, pCO2 40, pH 7.40
Initial cardiac markers: TnI of 1.21 ng/ml (99th percentile, 0.1 ng/ml)
Due to his symptoms and elevated cardiac Troponin I (cTnI), he underwent urgent coronary angiography which demonstrated only mild luminal irregularities, without an obvious culprit lesion. He was subsequently admitted for further evaluation.
Additional Diagnostic Tests:
Echo: Normal left and right ventricular wall motion and systolic function, no significant valvular abnormalities
Chest Xray: normal heart size, no air space disease.
Cardiac MRI-normal systolic function and wall motion, no late enhancement after gadolinium.
The most likely etiology for the troponin elevation is: