Association of High-Sensitivity Cardiac Troponin I Concentration With Cardiac Outcomes in Patients With Suspected Acute Coronary Syndrome

Abstract

Importance: High-sensitivity cardiac troponin I testing is widely used to evaluate patients with suspected acute coronary syndrome. A cardiac troponin concentration of less than 5 ng/L identifies patients at presentation as low risk, but the optimal threshold is uncertain.

Objective: To evaluate the performance of a cardiac troponin I threshold of 5 ng/L at presentation as a risk stratification tool in patients with suspected acute coronary syndrome.

Data sources: Systematic search of MEDLINE, EMBASE, Cochrane, and Web of Science databases from January 1, 2006, to March 18, 2017.

Study selection: Prospective studies measuring high-sensitivity cardiac troponin I concentrations in patients with suspected acute coronary syndrome in which the diagnosis was adjudicated according to the universal definition of myocardial infarction.

Data extraction and synthesis: The systematic review identified 19 cohorts. Individual patient-level data were obtained from the corresponding authors of 17 cohorts, with aggregate data from 2 cohorts. Meta-estimates for primary and secondary outcomes were derived using a binomial-normal random-effects model.

Main outcomes and measures: The primary outcome was myocardial infarction or cardiac death at 30 days. Performance was evaluated in subgroups and across a range of troponin concentrations (2-16 ng/L) using individual patient data.

Results: Of 11 845 articles identified, 104 underwent full-text review, and 19 cohorts from 9 countries were included. Among 22 457 patients included in the meta-analysis (mean age, 62 [SD, 15.5] years; n = 9329 women [41.5%]), the primary outcome occurred in 2786 (12.4%). Cardiac troponin I concentrations were less than 5 ng/L at presentation in 11 012 patients (49%), in whom there were 60 missed index or 30-day events (59 index myocardial infarctions, 1 myocardial infarction at 30 days, and no cardiac deaths at 30 days). This resulted in a negative predictive value of 99.5% (95% CI, 99.3%-99.6%) for the primary outcome. There were no cardiac deaths at 30 days and 7 (0.1%) at 1 year, with a negative predictive value of 99.9% (95% CI, 99.7%-99.9%) for cardiac death.

Conclusions and relevance: Among patients with suspected acute coronary syndrome, a high-sensitivity cardiac troponin I concentration of less than 5 ng/L identified those at low risk of myocardial infarction or cardiac death within 30 days. Further research is needed to understand the clinical utility and cost-effectiveness of this approach to risk stratification.

Figure 1.. Flow of the Study Population and Data Analysis

Flow diagram illustrating the systematic database review and screening of articles, level of exclusion, the number of articles included, and the individual patient-level data or aggregate data available for each analysis, based on the PRISMA-IPD guidelines. ^aArticles identified through a systematic database search: MEDLINE = 2078; EMBASE = 7116; Cochrane = 390; Web of Science = 2261. ^bAny identical publications were removed, but articles from the same cohorts were retained at this stage. ^cArticles excluded after full-text review because they evaluated a contemporary cardiac troponin I assay (n = 36), a different high-sensitivity cardiac troponin I assay (n = 14), a high-sensitivity cardiac troponin T assay (n = 5), a different patient population (n = 4), or a different outcome measure (n = 9). ^dAuthors who did not provide individual patient-level data provided aggregate data for the primary outcome, subgroup analyses, and secondary outcome when available. ^eSubgroup analyses were prespecified, with the following data available per group: age (n = 18 248), sex (n = 18 248), diagnosis of ischemic heart disease (n = 14 160), time from symptom onset to troponin sample time (n = 13 404), and electrocardiogram (n = 15 887).

Figure 2.. Negative Predictive Value of an hs-cTnI Concentration of Less Than 5 ng/L at Presentation by Cohort for Primary Outcome (Index Myocardial Infarction or Cardiac Death at 30 Days) by Assay Used for Adjudication

Data markers indicate the central estimate of negative predictive value (NPV) (orange markers for cardiac troponin I [cTnI] and black markers for cardiac troponin T [cTnT] assays) with size of the data markers corresponding to the number of patients per cohort (large, >3000 patients; medium, ≥1000 patients; small, <1000 patients) and error bars indicating 95% CIs. Dotted line indicates central estimate of NPV at 99.5%. ADAPT indicates 2-h Accelerated Diagnostic Protocol to Assess Patients With Chest Pain Symptoms Using Contemporary Troponins as the Only Biomarker; APACE, Advantageous Predictors of Acute Coronary Syndromes Evaluation; BACC, Biomarkers in Acute Cardiovascular Care; EDACS, Emergency Department Assessment of Chest Pain Score; High STEACS-P, High-Sensitivity Cardiac Troponin in the Evaluation of Patients With Suspected Acute Coronary Syndrome–Pilot; High STEACS-S; High-Sensitivity Cardiac Troponin in the Evaluation of Patients With Suspected Acute Coronary Syndrome–Substudy; High STEACS-V; High-Sensitivity Cardiac Troponin in the Evaluation of Patients With Suspected Acute Coronary Syndrome–Validation; hs, high sensitivity; IMPACT, Improved Assessment of Chest Pain Trial; RCT, randomized clinical trial; RING, Reducing the Time Interval for Identifying New Guideline; ROMI, Rule Out of Myocardial Infarction; TRUST, Triage Rule-Out Using High-Sensitivity Troponin; UTROPIA, Use of Abbott High Sensitivity Cardiac Troponin I Assay in Acute Coronary Syndromes.

Figure 3.. Negative Predictive Value of an hs-cTnI Concentration of Less Than 5 ng/L at Presentation for Primary Outcome (Index Myocardial Infarction or Cardiac Death at 30 Days) by Prespecified Subgroup

hs-cTnI indicates high-sensitivity cardiac troponin I; NPV, negative predictive value. Data markers indicate the central estimate of NPV with size corresponding to the number of patients per cohort (large, >3000 patients; medium, ≥1000 patients; small, <1000 patients) and error bars indicating 95% CIs. Dotted line and shaded areas represent the central estimate and 95% CIs for the full analysis population. All 19 cohorts were included in analyses unless otherwise specified. ^aIschemic heart disease status available in 16 of 19 cohorts. ^bTime from symptom onset to troponin sample collection available in 15 of 19 cohorts. ^cElectrocardiogram findings available in 15 of 19 cohorts.

Figure 4.. Optimal Threshold of hs-cTnI at Presentation to Risk-Stratify Patients With Suspected Acute Coronary Syndrome for Myocardial Infarction or Cardiac Death at 30 Days

hs-cTnI indicates high-sensitivity cardiac troponin I; NPV, negative predictive value. In all panels, performance of hs-cTnI thresholds are shown for all patients (dark blue) and when applied to patients with nonischemic electrocardiogram (ECG) findings at presentation (light blue). All estimates of NPV are derived from a binomial-normal random-effects model using individual patient-level data (available in 17 cohorts) for each hs-cTnI threshold (n = 18 601; eTable 5 in the Supplement). A, NPV across a range of hs-cTnI concentrations. Error bars indicate 95% CIs. Horizontal dotted line indicates prespecified target NPV of 99.5% and vertical dotted line indicates hs-cTnI concentration of less than 5 ng/L. B, Cumulative proportion of all patients with suspected acute coronary syndrome classified as low risk. Dotted vertical line indicates proportion of patients with hs-cTnI concentration of less than 5 ng/L. C, Number of false negatives per 1000 patients tested across a range of hs-cTnI thresholds. Electrocardiogram data were not available for 2929 patients (15.7%).