Key result
Serial POC cTnI testing over 3 hours using the LoD cut-off or T-MACS decision aid ruled out AMI with 98.1% sensitivity (95% CI 89.9-100.0%) and 99.5% negative predictive value.
Why the study?
POC cTn assays are less sensitive than laboratory assays, and the accuracy of using different POC cTnI assays with the T-MACS decision aid or alone needed evaluation.
Does the T-MACS decision aid combined with a point-of-care cardiac troponin I assay accurately diagnose acute myocardial infarction in adults with suspected ACS?
Observational (n=347)
Yes
Does the T-MACS decision aid combined with a point-of-care cardiac troponin I assay accurately diagnose acute myocardial infarction in adults with suspected ACS?
Effect estimate: Sensitivity 98.1% (95% CI 89.9% to 100.0%)
The T-MACS decision aid combined with a point-of-care cardiac troponin I assay over 3 hours demonstrates high negative predictive value for ruling out acute myocardial infarction, though wide confidence intervals necessitate further validation.
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.
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Alghamdi et al. (2020) conducted an observational in suspected ACS (n=347). Point-of-care cTnI (Cardio 3 Triage, Alere) and T-MACS decision aid vs. Serial laboratory-based cTn testing was evaluated on Adjudicated diagnosis of acute myocardial infarction (AMI) (Sensitivity 98.1%, 95% CI 89.9% to 100.0%). Serial POC cTnI testing over 3 hours using the LoD cut-off or T-MACS decision aid ruled out AMI with 98.1% sensitivity (95% CI 89.9-100.0%) and 99.5% negative predictive value.
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