One hs-cTnI measurement can safely rule out MI in early presenters

Background

A single measurement of cTn at presentation is a safe and effective method to rule out MI in patients presenting more than 2–3 h after symptom onset [1,2]. However, it is unclear whether a single test strategy is also useful in patients presenting within fewer hours of symptom onset.

Aim of the study

The study aim was to evaluate and externally validate the diagnostic performance of a single cTnI measurement at presentation in patients with suspected MI, stratified according to the time of symptom onset.

Methods

This was a secondary analysis of the High-STEACS (High-Sensitivity Troponin in the Evaluation of patients with suspected Acute Coronary Syndrome) trial, a multicenter, stepped-wedge, cluster-randomized controlled trial evaluating the implementation of a hs-cTnI assay in 48,282 consecutive patients with suspected ACS across 10 secondary and tertiary care hospitals in Scotland [3]. In this secondary analysis, 41,103 patients were included, of whom 12,595 (31%) underwent hs-cTnI sampling ≤3 h of symptom onset, 17,468 (42%) within 4–12 h, and 11,040 (27%) >12 h. An adjudicated diagnosis of STEMI was an exclusion criterion.

For external validation, data from 7088 participants of the APACE (Advantageous Predictors of Acute Coronary Syndromes Evaluation) study were used [4,5]. In this prospective, international, multicenter study, patients presenting to the emergency department with symptoms suggestive of MI were included, with the aim of improving the diagnosis of MI.

Thresholds for the limit-of-detection (2 ng/L), rule-out (5 ng/L), and sex-specific 99th centile (16 ng/L in women and 34 ng/L in men) were compared.

Outcomes

The primary endpoint was type I or 4b MI during the index presentation. The secondary endpoint was type I or 4b MI of CV death ≤30 days of the index presentation.

Main results

Rule-out of index MI

• Of the 12,595 patients who presented ≤3 h of symptom onset, 3728 (30%) had an MI.
• In patients presenting ≤3 h, a hs-cTnI threshold of 2 ng/L resulted in a greater sensitivity for predicting MI during the index presentation (99.4%; 95%CI: 99.2%–99.5%) and higher negative predictive value (NPV) (99.7%; 95%CI: 99.6%–99.8%), compared with the sensitivity (96.5%; 95%CI: 96.2%–96.8%) and NPV (99.3%; 95%CI: 99.1%–99.4%) of a 5-ng/L threshold.
• In patients presenting >3 h of symptom onset, the sensitivity and NPV were similar for both thresholds.
• The sensitivity of the sex-specific 99th centile threshold was lower in both early presenters (i.e., presenting ≤3 h) (71.4%; 95%CI: 70.6%–72.2%) and late presenters (i.e., presenting >12 h) (92.5%; 95%CI: 92.0%–93.0%).

MI or CV death within 30 days

• In patients who underwent testing ≤3 h of symptom onset, the sensitivity of a 2-ng/L threshold for predicting MI or CV death ≤30 days of the index presentation was 99.2% (95%CI: 99.0%–99.3%) and the NPV was 99.6% (95%CI: 99.4%–99.7%).
• A 5-ng/L threshold had both a lower sensitivity (95.9%; 95%CI: 95.6%–96.3%) and NPV (99.0%; 95%CI: 98.8%–99.2%).

External validation

• Results were validated in the external validation cohort.

Conclusion

References

Find this article online at Eur Heart J.