Patients of any age with elevated troponin levels have increased risk of mortality, particularly in the first weeks after the positive test result, a recent study found.
The retrospective cohort study included 257,948 consecutive patients from five cardiovascular centers in the United Kingdom who underwent troponin testing for any clinical reason in 2010 to 2017. The study assessed the association between the highest troponin level measured during a patient's hospital stay and three-year mortality risk. The troponin levels were standardized across centers as a multiple of each laboratory's 99th centile of the upper limit of normal. Results were published by The BMJ on Nov. 21.
During a median follow-up of 1,198 days (interquartile range, 514 to 1,866 days), 21.7% of the patients died. A troponin level above the upper limit of normal was associated with a threefold increase in mortality risk during follow-up (hazard ratio [HR], 3.2; 95% CI, 3.1 to 3.2). The association was stronger in younger patients (HR in those 18 to 29 years of age, 10.6 [95% CI, 8.5 to 13.3]; HR in those older than age 90 years, 1.5 [95% CI, 1.4 to 1.6]). Across all age groups, a high troponin level was associated with about 15 percentage points higher risk of mortality, with the risk being heavily concentrated in the first few weeks after testing.
In patients who weren't diagnosed with acute coronary syndrome (n=120,049) increasing troponin level and mortality risk had a direct relationship. However, for patients who did have acute coronary syndrome, there was an inverted U-shaped pattern, so that patients with a troponin level greater than 70 times the upper limit of normal actually had lower mortality. After multivariable adjustment, this pattern persisted only in the patients who were managed invasively. In those treated with noninvasive therapy, troponin level and mortality were directly correlated.
The authors noted that this inverted U-shaped pattern was unexpected. They suggested it could be attributed to changing case-mix at higher troponin levels, plus they noted a high proportion of these patients underwent an invasive procedure. The results of the study can help inform clinicians who receive troponin measurement results, the authors said, although they noted that there is no consensus on how best to manage patients with elevated troponin levels but not acute coronary syndrome.
“Although even weakly raised troponin levels had marked prognostic significance, clinical decisions should depend on the underlying disease and not simply on the degree of increase in troponin,” they wrote. The finding that mortality risk was particularly increased in the few weeks after testing does suggest that “a conservative wait and see approach may not be appropriate,” the authors said.
Limitations of the study include that it was retrospective and not necessarily able to account for all confounding factors. The study also didn't have any information about why patients' troponin levels were measured and the authors were not able to accurately distinguish acute from chronic myocardial injury.