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Predicting ACS in Patients with Troponin T Elevations
Clinical context is more important than troponin level when interpreting a positive test.
Troponin is detectable at very low levels, but a troponin "leak" does not always mean that an acute coronary syndrome (ACS) is present. To determine predictors of ACS in the presence of an abnormal troponin level, investigators studied 635 patients who had positive (>0.1 ng/mL) troponin tests during a 9-month period at two Israeli hospitals.
Two experts reviewed charts and retrospectively assigned a diagnosis of ACS (according to European Society of Cardiology/American College of Cardiology guidelines) to 53% of patients and a nonthrombotic cause to 41% (these patients had a definitive diagnosis of a condition known to cause troponin elevation, such as sepsis or pulmonary embolism). The diagnosis was unknown in 6%. Mean troponin T levels were 1.5 ng/mL in patients with ACS and 0.6 ng/mL in those with nonthrombotic causes.
The positive predictive value (PPV) of a positive troponin T test for the diagnosis of ACS was only 56% overall and 48% when the troponin level was between 0.1 and 1.0 ng/mL. In multivariate analysis, age, renal function, and troponin level were strongly associated with a diagnosis of ACS. In patients older than 70 with abnormal renal function, the PPV of a troponin level between 0.1 and 1.0 ng/mL was 27%. In patients of the same age with normal renal function and a troponin level greater than 1.0 ng/mL, the PPV was 90%. Inhospital mortality rates were nearly eight times higher in patients with nonthrombotic causes than in those with ACS.
Comment: This study addresses a common problem in the emergency department: the finding of a small troponin "leak" that seems not to be associated with ACS. Troponin elevation mandates admission, regardless of presumed cause, as even small elevations are associated with high mortality rates, and non-ACS elevation portends a worse prognosis than ACS elevation. Emergency physicians should never be persuaded to send patients home because "it’s just a troponin leak."
— J. Stephen Bohan, MD, MS, FACP, FACEP
Published in Journal Watch Emergency Medicine March 9, 2007
Citation(s):
Alcalai R et al. Acute coronary syndrome vs nonspecific troponin elevation: Clinical predictors and survival analysis. Arch Intern Med 2007 Feb 12; 167:276-81.
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