Objective Point-of-care (POC) cardiac troponin (cTn) assays have a rapid turnaround time but are generally less sensitive than laboratory-based assays. Previous research found that the Abbott i-Stat cardiac troponin I (cTnI) assay has good diagnostic accuracy when used with the Troponin-only Manchester Acute Coronary Syndromes (T-MACS) decision aid and serial sampling over 3 hours. Accuracy of other assays may differ. We therefore evaluated the diagnostic accuracy of a different POC cTnI assay with serial sampling over 3 hours, both with T-MACS and when used alone.
Methods In a prospective diagnostic accuracy study at eight EDs in England (July 2015–October 2017), we collected clinical data from consenting adults with suspected ACS at the time of assessment in the ED. Blood samples were drawn on arrival and 3 hours later for POC cTnI (Cardio 3 Triage, Alere). The target condition was an adjudicated diagnosis of acute myocardial infarction (AMI), based on reference standard serial laboratory-based cTn testing. We calculated test characteristics for POC cTnI using the limit of detection (LoD, 0.01 µg/L) and the T-MACS decision aid.
Results Of 347 participants, 59 (14.9%) had AMI. With serial POC cTnI testing over 3 hours, POC cTnI at the LoD cut-off ruled out AMI in 193 (55.6%) patients with 98.1% sensitivity (95% CI 89.9% to 100.0%) and 99.5% negative predictive value (NPV, 95% CI 96.5% to 99.9%). T-MACS ruled out AMI in 117 (33.7%) patients with 98.1% sensitivity (95% CI 89.9% to 100%) and 99.2% NPV (95% CI 94.3% to 99.9%). T-MACS ruled in AMI with 97.9% specificity (95% CI 95.8% to 99.5%) and 83.7% positive predictive value (95% CI 70.6% to 91.7%).
Conclusions With serial sampling over 3 hours, the Alere Cardio 3 Triage cTnI assay has relatively high NPV for AMI using either the LoD cut-off alone or the T-MACS decision aid. However, wide CIs around the measures of diagnostic accuracy mean that further prospective testing of this strategy is required before clinical implementation.
Trial registration number UKCRN 18000.
- acute coronary syndrome
- acute myocardial infarct
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Contributors AA drafted the manuscript. AA and CR performed the analysis and designed the figures. NM and RB designed and conducted the study. PM, HJ, EH, TH, DH and RP contributed to the data collection and implementation of the clinical study. All authors contributed substantially to this work, the revision and final approval of the manuscript, and meet the International Committee of Medical Journal Editors (ICMJE) criteria for authorship.
Funding The Bedside Evaluation of Sensitive Troponin study received funding from Abbott Point of Care, European Union Horizons-2020 (via FABPulous BV), the Royal College of Emergency Medicine and Alere (donation of reagents for research).
Competing interests AA and RB received funding from Abbott Point of Care and donation of reagents from Roche Diagnostics International Ltd and LumiraDx. RB received speaker fees from Singulex, Roche (consultancy and research grant), Abbott Point of Care (speaker fee and research grant), FABPulous BV (consultancy) and Alere (donation of reagents for research).
Patient consent for publication Not required.
Ethics approval The study was approved by the National Research Ethics Service (reference 14/NW/1344), was sponsored by Manchester University NHS Foundation trust and was undertaken in full compliance with the Declaration of Helsinki and according to the principles of good clinical Practice. All participants provided written informed consent.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Unpublished data are available upon reasonable request. Please contact Professor Richard Body at firstname.lastname@example.org.
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