Novel hs-cTn Assay with a Single Serum Test in ED.

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Objectives

To evaluate diagnostic accuracy of a high-sensitivity cardiac troponin I (hs-cTnI) assay for acute coronary syndromes (ACS) in the Emergency Department (ED). The assay has high precision at low concentrations and can detect cTnI in 96.8% of healthy individuals. 

Methods

In successive prospective multi-center studies (‘testing’ and ‘validation’) we included ED patients with suspected ACS. We drew blood for hs-cTnI (Singulex Clarity® cTnl, 99th percentile 8.67ng/L, limit of detection [LoD] 0.08ng/L) on arrival. Patients also underwent hs-cTnT (Roche Elecsys) testing over ≥3h. The primary outcome was an adjudicated diagnosis of ACS, defined as acute myocardial infarction (AMI; prevalent or incident), death, or revascularization within 30 days.

Results

The testing and validation studies included 665 and 2,470 patients respectively, of which 94 (14.1%) and 565 (22.9%)  had ACS. At a 1.5ng/L cut-off, hs-cTnI had good sensitivity for AMI in both studies (98.7% and 98.1% respecively) and would have ‘ruled out’ 40.1% and 48.9% patients. However, sensitivity was lower for ACS (95.7% and 90.6% respectively). At a 0.8ng/L cut-off sensitivity for ACS was higher (97.5% and 97.9%, ‘ruling out’ 28.6% patients in each cohort). The hs-cTnT assay had very similar performance at the LoD (24.6% ‘ruled out’, 97.2% sensitivity for ACS).

Conclusion 

The hs-cTnI assay could immediately ‘rule out’ AMI in 40% patients and ACS in over 25%, with similar accuracy to hs-cTnT at the LoD. Because of its high precision at low concentrations, this hs-cTnI assay has favourable characteristics for this clinical application.

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