Diagnostic Utility of Creatine Kinase in Patients Presenting to the Emergency Department with Chest Pain

Abstract

Introduction: Creatine Kinase (CK) is routinely performed in some emergency departments (ED) for Non-ST-elevation myocardial infarction (NSTEMI) workup. Its diagnostic utility is not well understood. The objectives of this study were to assess the value of CK in NSTEMI diagnosis in the troponin era and the association between the highest CK/Troponin values and ejection fraction (EF) during NSTEMI follow-up.    Methods: A prospective cohort study conducted at the two EDs of The Ottawa Hospital from March 2014 to March 2016 enrolled adults (≥18 years) for whom troponin I (TnI) and CK were ordered for NSTEMI symptoms. We excluded those with ST-Elevation Myocardial Infarction (STEMI). The primary outcome was a NSTEMI within 30 days. We used descriptive statistics and report test diagnostic characteristics with 95% confidence intervals (CI). We compared the highest median CK/Troponin values using Wilcoxon test.   Results: Of the 2,153 patients enrolled, 99 (4.6%) suffered a NSTEMI. The sensitivity and specificity were: CK (cutoff >250U/L) 31.3% (95%CI 22.2, 40.5) and 91.1% (95%CI 89.9, 92.4) respectively; TnI (cutoff >0.045µg/L) 98.0% (95%CI 95.2, 100) and 86.2% (95%CI 84.7, 87.7) respectively. The median CK values were not significantly different between those with normal (n=267) and abnormal EF (n=55) on follow-up (107 U/L and 118 U/L respectively; p=0.31), whereas the median TnI values were significantly different (0.02 µg/L and 0.1 µg/L respectively; p<0.0001).   Conclusions: CK measurements do not provide any value in the ED work-up of NSTEMI and is not associated with EF on follow-up. Discontinuing routine CK measurements would improve resource utilization.