Abstract
BACKGROUND: In emergency department (ED) patients with renal impairment, troponin concentrations can be positive without myocardial ischemia. When there is clinical concern for acute coronary syndrome (ACS), guidelines recommend obtaining a delta troponin measurement to identify acute myocardial injury. However, evidence supporting the use of delta troponin to rule in or out ACS in patients with renal impairment and initial elevated troponin levels is limited. METHODS: This retrospective, observational study assessed the diagnostic value of a 20% delta troponin cutoff in the prediction of ACS events in ED patients (estimated glomerular filtration rate [eGFR] <60 mL/min/1.72 m(2)) with renal impairment, clinical concern for ACS, and an initial positive troponin concentration using either conventional troponin (cTnT) or high-sensitivity troponin (hsTnT). Clinical concern for ACS was based on initial ED physician-reported diagnoses. Patients with an initial diagnosis of ST-elevation myocardial infarction were not included. A positive initial troponin was identified at a threshold of ≥0.06 ng/mL for cTnT and ≥52 ng/L for hsTnT, and delta troponin measurements were obtained within 24 h of the initial troponin. The primary composite outcome, termed ACS event, included (1) cardiac-related mortality, (2) coronary revascularization (or its recommendation), or a (3) clinically diagnosed type-1 myocardial infarction within 6 weeks of the ED presentation. Sensitivities, specificities, negative predictive values, positive predictive values, and negative and positive likelihood ratios were calculated for these 6-week ACS events. RESULTS: A total of 608 ED patients with renal impairment, an initial positive troponin, and clinical concern for ACS were included in the study. Of these patients, 234 had an initial positive cTnT (median eGFR 18 mL/min/1.72 m(2)) and 374 had an initial positive hsTnT (median eGFR 25 mL/min/1.72 m(2)). The overall ACS event rate was 38% in the cTnT group and 33% in the hsTnT group. In those with a negative delta, the 6-week ACS event rate was 32% when using cTnT, compared to 24% using hsTnT. Conversely, a positive delta was associated with an ACS event rate of 47% when cTnT was utilized versus 61% when hsTnT was utilized. CONCLUSION: In this study, approximately one-third of ED patients with renal impairment who had an initial positive troponin and clinical concern for ACS developed ACS events at 6 weeks. A delta troponin did not appear to provide clinically meaningful assistance in the prediction or exclusion of 6-week ACS events in this cohort.