Objectives: We evaluated a third-generation high sensitivity "guidelines acceptable" troponin I assay (hs-cTnI) against a contemporary "clinically usable" troponin assay (cTnI).
Design and methods: Remnant samples of undifferentiated emergency department (ED) patients with suspected acute coronary syndrome were enrolled. Baseline and 90-minute samples were analyzed for cTnI and hs-cTnI. Sensitivity, specificity, positive and negative predictive values for AMI and 30-day adverse cardiac events (ACE) were compared.
Results: Of 486 ED patients, there were 465 patients who had blood remaining at the presentation for the hs-cTnI assays, with 12 AMIs. At presentation, the clinical sensitivity and specificity for AMI was 75% and 97% for cTnI and 83.3 and 82.1% for hs-cTnI. There were 407 patients who had paired baseline and 90-minute blood samples for cTnI and hs-cTnI including 9 of the 12 AMI patients. The sensitivity and specificity was 77.7% and 96.5% for cTnI and 100% and 81.9% for hs-cTnI at 90 min. A Δ change of 30% increase from baseline to 90 min improved the specificity to 94.5% (95% CI 92%-96%) without lowering the sensitivity. When AMI was defined as a Δ30% change of hs-cTnI at t=0 and 90 min and one hs-cTnI result >99th percentile cutoff, more than 3 times as many patients met the diagnostic criteria for AMI compared to results from the normal sensitive troponin assay; 28 (6.9%) for hs-cTnI vs. 9 (2.2%) with cTnI. There were 37 in-hospital or 30-day events, producing an OR of 3.03, 95% CI: 0.86-9.59 for cTnI, and 2.54, 95% CI: 1.27-5.10 for hs-cTnI, which detected 11 more cases.
Conclusions: The hs-cTnI assay achieved a 90-minute rule out for AMI and detected more 3 times as many AMI cases. The specificity increased with the Δ30% criteria. The hs-cTnI assay also detected more cases of patient at risk for adverse cardiac events at 30 days.
Copyright © 2012 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.