Abstract 1791: Delta Measurements of an Ultrasensitive Troponin I Assay Reliably Diagnose the Full Spectrum of Acute Coronary Syndromes and Predict Adverse Cardiac Events Within 30 Days of ED Visits
Objective: New ultrasensitive cTnI assays lack specificity for acute coronary syndromes (ACS) at the lower limits of detection (LLD). We hypothesized that delta cTnI calculations would improve the specificity in diagnosing index visit (IV) and 30 day adverse cardiac events (ACE) in ED pts and identify a subset of pts with very low risk of ACE- MI, urgent revascularization (UR), or death within 30 days, using cTnI assays alone.
Methods: This is a retrospective study of 275 consecutive ED pts whose work up included at least 3 cTnI measurements. Prehospital arrest pts were excluded. Setting: Level 1 academic ED volume of 60,000 pts per year. cTnI was measured using the Abbot Architect assay (LLD: 0.02 ng/ml (cv 10%)). Samples were drawn at 0, 4, and 8 hours from arrival. Chart review and phone follow up were conducted for: any ACS on IV or ACE within 30 days. The Social Security Death Index (SSDI) was checked on all pts for whom 30 day follow up was unobtainable. ROC curve analysis was used to determine the optimal cut points for peak and delta cTnI for diagnosis and prognosis of ACS and ACEs.
Results: Of the 275 pts, 10 (3.6%) were lost to follow up. SSDI search revealed that 3 pts died within 30 days of hospital visit (2- strokes; 1- multiple medical problems). Data on the remaining 262 pts were analyzed to determine predictive values of the serial cTnI measurement. There were 47 ACS events (17.1%) during the IV and 5 ACEs (1.8%) during the follow up period. Areas under the curve (AUC) for peak cTnI were 0.848 and 0.853, for events on IV and within 30 days, respectively. AUC for delta cTnI were 0.892 and 0.891, for events on IV and within 30 days, respectively. In the 69 pts with 3 undetectable cTnI, only 1 pt (1.4%) underwent UR within 30 days; there were no deaths or MIs.
Conclusion: This new cTnI assay demonstrates high sensitivity for the full range of ACS, not limited to MI. Delta cTnI calculations significantly improve specificity. These data are significantly improved over prior published reports.