Can a single nondetectable high-sensitivity cardiac troponin T measurement be used to rapidly rule out acute myocardial infarction?

A single high-sensitivity cardiac troponin T (hs-cTnT) result below the limit of detection, in combination with a electrocardiogram showing no acute ischemia, is effective in ruling out acute myocardial infarction (AMI) in an emergency setting. A single elevated result, though, has low positive predictive value. (LOE = 1a-)

Pickering JW, Than MP, Cullen L, et al. Rapid rule-out of acute myocardial infarction with a single high-sensitivity cardiac troponin T measurement below the limit of detection. A collaborative meta-analysis. Ann Intern Med 2017;166(10):715-724.  [PMID:28418520]

Meta-analysis (other)

Foundation

Emergency department

These researchers searched 2 databases to find research in any language that assessed the use of hs-cTnT to evaluate patients presenting to an emergency department with acute coronary syndrome. They identified 11 studies of 9241 patients; 2825 of whom were classified as low risk (ie, no new ischemia on cardiogram and hs-cTnT measurements of less than .005 mcg/L). The main outcome of the studies was the number of patients who had AMI during hospitalization, though the authors also evaluated the likelihood of a major adverse cardiace event (MACE) or death within 30 days in patients at low risk or not low risk. Fourteen (0.5%) patients classified as low risk had AMI. The sensitivity of the combination of cardiogram findings and nondetectable hs-cTnT (the ability to rule out AMI if negative) was 98.7% (95% CI 96.6% - 99.5%). The sensitivity for MACE was similarly 98.0% (94.7% - 99.3%). No low-risk patients died. These data translate into a typical negative predictive value of greater than 99%. A single hs-cTnT has very low specificity and cannot be relied on to identify patients with AMI or those at risk for a major cardiovascular event. This meta-analysis used patient-level data, which is good. The analysis suffers, though, because of individual study quality, primarily because the selective enrollment of patients into the majority of the studies resulted in high heterogeneity among the study results. The meta-analysis authors also had to exclude a number of studies because of a recalibration of the assay by its manufacturer.