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.

重要性  高灵敏度的心肌肌钙蛋白I检测被广泛用于评估可疑的急性冠状动脉综合征的患者。心脏肌钙蛋白浓度低于5 ng / L时，将患者确定为低风险患者，但最佳阈值尚不确定。

目的  评估可疑急性冠状动脉综合征患者风险时，作为危险分层工具的心脏肌钙蛋白I阈值为5 ng / L的表现。

数据  源自2006年1月1日至2017年3月18日，系统搜索MEDLINE，EMBASE，Cochrane和Web of Science数据库。

研究选择  前瞻性研究测量疑似急性冠状动脉综合征患者的高敏感性心肌肌钙蛋白I浓度，其中根据心肌梗塞的普遍定义对诊断作出了判断。

数据提取和综合  系统评价确定了19个队列。个体患者水平数据来自17个队列的相应作者，以及2个队列的汇总数据。使用二项式正常随机效应模型得出主要和次要结局的荟萃估计。

主要结果和措施  主要结果为30天时的心肌梗塞或心源性死亡。使用单独的患者数据，在亚组中以及在一系列肌钙蛋白浓度（2-16 ng / L）中评估了表现。

结果  在确定的11 845篇文章中，有104篇进行了全文审查，其中包括来自9个国家的19个队列。纳入荟萃分析的22457例患者（平均年龄62岁[SD，15.5]岁； n = 9329名女性[41.5％]），主要结局发生在2786例中（12.4％）。在11 012例患者中，表现出的肌钙蛋白I浓度低于5 ng / L（49％），其中有60项指标缺失或30天事件（59指标心肌梗死，30天内1例心肌梗死，无心脏） 30天死亡）。这导致主要结局的阴性预测值为99.5％（95％CI，99.3％-99.6％）。30天无心脏死亡，1年无7例心脏死亡（0.1％），心源性死亡的阴性预测值为99.9％（95％CI，99.7％-99.9％）。

结论和相关性  在怀疑为急性冠脉综合征的患者中，高敏感性心肌肌钙蛋白I浓度低于5 ng / L可以识别出在30天内具有低心肌梗塞或心源性死亡风险的患者。需要进一步的研究来了解这种方法用于风险分层的临床效用和成本效益。