A single value of high-sensitive troponin T below the limit of detection is not enough for ruling out non ST elevation myocardial infarction in the emergency department

Abstract

Background: Recent 2015 ESC recommendations for the management of patients with suspected acute myocardial infarction (AMI) support that a single value of high-sensitivity cardiac troponin (HS-cTn) measured at presentation could rule out AMI if below the limit of blank (LoB) or detection (LoD).

Objectives: We aimed to evaluate whether an undetectable HS-cTnT at presentation safely rules out NSTEMI in unselected patients with chest pain.

Patients and methods: This is a post hoc analysis of two prospective cohorts with similar design that included patients suspected of AMI at three French university hospitals. Patients were followed-up during one month, before the adjudication of a final diagnosis.

Results: 413 patients (mean age 58±17years) were analyzed; 45 (11%) had a final diagnosis of NSTEMI, and 26 (6%) had STEMI. The sensitivity of HS-cTnT value at 3ng/L (LoB) for NSTEMI was 97.8% [95% CI: 86.8-99.9], yielding a negative predictive value (NPV) of 99.3% [95% CI: 95.4-100.0]. Proportion of patients ruled out for NSTEMI was 32% when applying the LoB. The sensitivity of HS-cTnT value at 5ng/L (LoD) was 97.8% [95% CI: 86.8-99.9] yielding a NPV of 99.5% [95% CI: 96.5-100.0]. Proportion of patients ruled out for NSTEMI was 43% when applying the LoD. One patient (delay between onset of chest pain and presentation <3h) had NSTEMI and HS-cTnT <LoB at presentation.

Conclusion: The NPV of a single measurement of HS-cTnT below the LoD is high in unselected patients, but not enough to rule out safely NSTEMI for very early presenters.

Keywords: Acute coronary syndrome; Acute myocardial infarction; Chest pain; Emergency department; High sensitive troponin.