Suspected myocardial infarction in the emergency department: An evaluation of clinical thresholds for the Beckman Coulter Access hsTnI high‐sensitivity cardiac troponin I assay

Objective The primary objective was to determine rapid rule‐out (RRO) criteria for the outcome of myocardial infarction (MI) using the Beckman Coulter Access high‐sensitivity cardiac troponin I (hs‐cTnI) assay. Secondary objectives were to explore cut‐points for rapid rule‐in (RRI) and amount of change at 3‐h (3‐h delta) indicative of MI. Methods A retrospective study included ED patients with suspected MI between June and September 2019. hs‐cTnI levels were performed at baseline and after 3 h. The performance benchmark for RRO criteria was a negative predictive value (NPV) for MI with a lower 95% confidence limit >99%, and for RRI and 3‐h delta cut‐points was a positive predictive value (PPV) for MI >70%. Delta calculation required rising hs‐cTnI levels, with at least one above the 99th percentile of the upper reference limit. Analyses utilised receiver operating characteristic (ROC) curves and contingency tables. Results Baseline hs‐cTnI levels from 935 patients were available for RRO analyses. Of tested criteria, baseline hs‐cTnI <6 ng/L (females) or <11 ng/L (males) plus symptom onset >2 h met the performance benchmark (NPV: 100% [95% confidence interval 99–100]). hs‐cTnI levels were available for RRI and 3‐h delta analyses from 935 and 52 patients, respectively. A 3‐h delta cut‐point >35 ng/L met the performance benchmark (PPV: 81% [95% confidence interval 58–95]) but no RRI cut‐point did so. Conclusions For the Beckman Coulter Access hs‐cTnI assay, RRO criteria of baseline hs‐cTnI <6 ng/L (females) or <11 ng/L (males) plus symptom onset >2 h met our performance benchmark. A 3‐h delta cut‐point >35 ng/L met the performance benchmark, but poor precision means further adequately powered research is required.