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Early Diagnosis of MI With Point-of-Care hs-cTnI
Study Questions:
How does the diagnostic accuracy of an emergency department (ED) point-of-care high-sensitivity troponin I (POC-hs-TnI) assay compare to established central laboratory assays?
Methods:
The APACE (Advantageous Predictors of Acute Coronary Syndromes Evaluation) is an ongoing prospective international multicenter study that assesses methods for the early diagnosis of myocardial infarction (MI). In this substudy of APACE, 1,261 patients presenting to the ED with suspected MI had measurement of POC-hs-TnI by TriageTrue in addition to central laboratory hs-Tn assays (hs-TnT-Elecsys by Roche Diagnostics, hs-TnI-Architect by Abbott Laboratories), following the 0/1-hour algorithm. The POC-hs-cTnI TriageTrue assay on the Triage MeterPro System has an overall 99th percentile concentration of 20.5 ng/L (women 14.4 ng/L, men 25.7 ng/L) with an overall coefficient of variation of 5.6%. The authors identified cut-off concentrations for low-risk MI defined by a negative predictive value of ≥99.5% and sensitivity of ≥99%, and for rule-in of MI with a positive predictive value of ≥75%, and specificity of ≥95%. Cut-offs were then applied to an internal validation cohort of 545 patients.
Results:
Of 1,261 patients, 32% were women and 39% presented within 3 hours after the onset of chest pain. The median age of the population was 60 years. There was a total of 178 (14%) adjudicated MIs. The median concentration of POC-hs-TnI was 109 ng/L (interquartile range of 25-425 ng/L) in patients with MI. There was a high correlation among all three assays (r > 0.8). The diagnostic accuracy of POC-hs-TnI as assessed by area under the curve (0.95) was similar to that of hs-TnT-Elecsys (0.94) and hs-TnI-Architect (0.92), and did not differ in subgroups, notably gender and early versus late presenters. A cut-off of POC-hs-TnI <5 ng/L at presentation and absolute change <3 ng/L met the predefined criteria for MI rule-out, while >60 ng/L or absolute change at 1 hour of ≥8 ng/L met the criteria for MI rule-in. The cut-offs showed consistent negative predictive value and positive predictive value for rule-out and rule-in MI in the validation cohort. No patient with an index MI was missed using these cut-offs.
Conclusions:
A POC-hs-TnI assay performed comparably to central laboratory assays in the rule-in and rule-out of MI of patients presenting to the ED with chest pain.
Perspective:
Point-of-care assays are highly sought as a strategy to rapidly and cost-effectively diagnose or rule-out MI. Until recently, the assays lacked sensitivity compared to central laboratory assays. This study allays concerns of performance and safety of a POC-hs-TnI assay that could be easily and rapidly deployed; minimizing the logistical challenges of smaller healthcare systems in adopting a 0/1-hour MI rule-out algorithm. The next step in diagnostic testing for MI will be integration of hs-Tn in emergency medical services and first-responders.
Clinical Topics: Acute Coronary Syndromes, Cardiovascular Care Team, Prevention, ACS and Cardiac Biomarkers
Keywords: Acute Coronary Syndrome, Algorithms, Biomarkers, Chest Pain, Early Diagnosis, Emergency Service, Hospital, Myocardial Infarction, Point-of-Care Systems, Secondary Prevention, Triage, Troponin, Troponin I
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