There was strong evidence to support using a single high-sensitivity cardiac troponin T (hs-cTnT) test with a limit of detection (LoD) of 5 ng/L to rule out acute myocardial infarction. According to the Food and Drug Administration (FDA) of the United States (US), hs-cTnT can only report to a limit of quantitation (LoQ) of 6 ng/L, a level for which there is limited data. For a study, researchers sought to determine if a single hs-cTnT below the LoQ of 6 ng/L was a safe way to identify people at low risk of acute myocardial damage and infarction.
The effectiveness of identifying low-risk individuals (based on baseline hs-cTnT<6 ng/L) was investigated in a multicenter (n=22 locations) US cohort trial of emergency department patients having at least one hs-cTnT test (CV Data Mart Biomarker cohort). The performance of a single hs-cTnT<6 ng/L (biomarker alone) to exclude acute myocardial damage was then assessed (subsequent hs-cTnT >99th percentile in individuals with an initial hs-cTnT<6 ng/L). The clinically intended rule-out technique, which combined a nonischemic ECG with a baseline hs-cTnT<6 ng/L, was then assessed in an adjudicated cohort to assess diagnostic performance for ruling out acute myocardial infarction and safety (myocardial infarction or mortality at 30-days).
In the CV Data Mart Biomarker cohort, 85,610 individuals were assessed, with 24,646 (29%) having a baseline hs-cTnT<6 ng/L. Women were more likely than males to have hs-cTnT<6 ng/L (38% vs. 20%, P<0.0001). Only 1.2% of 11,962 patients with baseline hs-cTnT<6 ng/L and serial measures had acute myocardial damage, yielding a negative predictive value of 98.8% (95% CI 98.6, 99.0) and sensitivity of 99.6% (95% CI 99.5, 99.6). A nonischemic ECG with hs-cTnT<6 ng/L classified 33% of patients (610 of 1849) as low-risk, with a negative predictive value and sensitivity of 100%, and a 30-day rate of 0.2% for 30-day myocardial infarction or death. A single hs-cTnT level below the LoQ of 6 ng/L provided a safe and quick way to identify a large number of people with an extremely low risk of acute myocardial damage and infarction.