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001 High sensitivity troponin: validation and subsequent audit of a novel “rule out” cut-off
  1. R Body1,2,
  2. G Burrows2,
  3. G Cook2,
  4. S D Carley3,
  5. M France3,
  6. J Jarvis2,
  7. B Haves2,
  8. P S Lewis2
  1. 1Cardiovascular Sciences Research Group, Manchester, UK
  2. 2Emergency Department, Stockport NHS Foundation Trust, Manchester, UK
  3. 3Department of Laboratory Medicine, Central Manchester NHS Foundation Trust, Manchester, UK

Abstract

Objectives and Backgrounds High sensitivity troponin (hs-Tn) has been shown to improve early diagnosis of acute myocardial infarction (AMI). We recently reported that levels below the limit of blank (LoB, <3 ng/l) of the Roche assay had 100.0% negative predictive value (NPV). Now, we aim to validate that finding in (i) a cohort study and (ii) routine clinical use following implementation.

Methods Initially, we included adult emergency department (ED) patients with suspected cardiac chest pain in a prospective diagnostic cohort study. Standard troponin T (TnT) and hs-TnT (Roche) were tested at presentation. The primary outcome was a diagnosis of AMI, adjudicated by two independent investigators based on reference standard ≥12 h TnT testing. Secondary outcomes included AMI defined by ≥12 h hs-TnT. After clinically implementing hs-TnT at a different institution, we identified all patients undergoing ≥2 hs-TnT tests within 24 h and evaluated initial hs-TnT level for predicting any subsequent rise.

Results 477 patients were included in the cohort study. 475 (99.6%) underwent reference standard testing. 82 (17.3%) had AMI. The area under the ROC curve was 0.95 (95% CI 0.92 to 0.97) for hs-TnT compared to 0.84 (0.78 to 0.90) for TnT (p=0.001). At the 99th percentile, sensitivity was 93.9% (86.3% to 98.0%) for hs-TnT and 70.7% (59.7% to 80.3%) for TnT (p<0.0001; Abstract 001 table 1). At the LoB (<3 ng/l) cut-off, sensitivity of hs-TnT was 98.8% (93.4% to 100.0%) with NPV 99.2% (95.5% to 100.0%). Using ≥12 h hs-TnT to define AMI, sensitivity of initial hs-TnT<3 ng/l was 99.4% (96.5% to 100.0%). On subsequently appraising hs-TnT in 915 patients in clinical practice, sensitivity (at the LoB) was 99.8% (99.1% to 100.0%) with NPV 99.4% (96.6% to 100.0%).

Abstract 001 Table 1

Diagnostic performance of hs-TnT (at each cut-off) and cTnT in the cohort study and subsequent audit in clinical practice

Conclusions This work again demonstrates that hs-TnT improves sensitivity for AMI in the ED. Undetectable hs-TnT (<3 ng/l) levels have very high NPV, a strategy that has now been prospectively validated in both research and clinical practice populations. A randomised controlled trial of early discharge using hs-TnT is being planned.

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