BACKGROUND: Guidelines for diagnosing acute myocardial infarction (AMI) recommend adding kinetic changes to the initial cardiac troponin (cTn) blood concentration to improve AMI diagnosis. We hypothesized that kinetic changes may not be required in patients presenting with highly abnormal cTn.
METHODS: Patients presenting with suspected AMI to the emergency department were enrolled in a prospective diagnostic study. We assessed the positive predictive value (PPV) of initial high-sensitivity cardiac troponin T (hs-cTnT) blood concentrations alone and in combination with kinetic changes for AMI. Predefined relative changes (δ change of ≥20%) and absolute changes (Δ change ≥9.2 ng/L) within different time intervals (1 h, 2 h, and 4–14 h after presentation) were assessed. The final diagnosis was adjudicated by 2 independent cardiologists.
RESULTS: Among 1282 patients, 213 (16.6%) patients had a final diagnosis of AMI. For AMI prediction, PPVs increased from 48.8% for an initial hs-cTnT >14 ng/L to 87.2% for >60 ng/L, whereas PPVs remained unchanged for higher hs-cTnT concentrations at baseline (87.1% for both >80 ng/L and >100 ng/L). With addition of 20% relative Δ change, PPVs were not further improved in patients with baseline hs-cTnT >80 ng/L using the 1-h (84.0%) and 2-h (88.9%) intervals, and only minimally when extending the interval to 4–14 h (91.2% for >80 ng/L and 90.4% for >100 ng/L, respectively). Similar findings were observed when applying absolute changes.
CONCLUSIONS: In chest pain patients with highly abnormal hs-cTnT concentrations at presentation, subsequent blood draws may not be required, as they do not provide incremental diagnostic value for prediction of AMI diagnosis.
- Received for publication April 1, 2016.
- Accepted for publication August 9, 2016.
- © 2016 American Association for Clinical Chemistry