Written by Megan Hilbert
A single high sensitivity cardiac troponin T (hs-cTnT) measurement* less than the limit of quantitation (the lowest reportable concentration) appears to be sufficient in ruling out acute MI in a low risk population.
Why does this matter?
A shift in the ER is not complete without at least one patient with chest pain, and this complaint represents 6.5 million ED visits per year. With new high sensitivity troponin assays, it is easier than ever to rule out acute myocardial infarct with a single troponin** measurement. This can greatly reduce ED length of stay and cost associated with a cardiac work-up.
With a negative troponin, am I positive that I can get my patient out?
This was a multi-center cohort study with both a biomarker and observational component. Previous literature has demonstrated safety in ruling out severe pathology with hs-cTnT level less than 5ng/L. Unfortunately, the FDA has determined that hs-cTnT, “can only report to the limit of quantitation of 6ng/L,” in the US. With limited data established at this level, this study aimed to prove the efficacy and safety of hs-cTnT <6ng/L at ruling out acute cardiac injury in low risk patients. Secondary analyses evaluated the clinical application of this approach in combination with non-ischemic ECGs, with particular attention paid to diagnostic accuracy and 30-day safety.
Results were overwhelmingly encouraging, with a NPV of 99.8% (95%CI, 99.1-100) and sensitivity 99.3% (95%CI, 96.1-100)*** using a single negative hs-cTnT in isolation. NPV and sensitivity both increased to 100% when combining a negative hs-cTnT with a non-ischemic ECG. These data represent a 0.3% missed diagnosis rate of acute MI or death within 30 days. While the medical community has yet to establish an “acceptable” miss rate for cardiac injury, this is pretty darn good. Further subgroup analysis revealed that NPVs were lower in patients with history of CAD, older adults, and women, which serves as a warning that caution should be taken with these populations.
Rapid Exclusion of Acute Myocardial Injury and Infarction With a Single High-Sensitivity Cardiac Troponin T in the Emergency Department: A Multicenter United States Evaluation. Circulation. 2022 Jun 7;145(23):1708-1719. doi: 10.1161/CIRCULATIONAHA.122.059235. Epub 2022 May 10.
*Please note that these data were performed with the Elecsys Troponin T Gen 5 STAT assay. Studies will need to be completed to evaluate the safety and efficacy of ruling out cardiac pathology with other assays.
**The European Society of Cardiology (ESC) has endorsed single troponin algorithms for rule out of acute MI in low-risk patients as a class I recommendation since 2015. The American Heart Association and American College of Cardiology currently support this approach with class 2a recommendations (level of evidence B, non-randomized)
***If you want the gory details, Tables 2 and 3 below have them.