Performance of high-sensitivity cardiac troponin in the emergency department for myocardial infarction and a composite cardiac outcome across different estimated glomerular filtration rates
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BACKGROUND: Clinicians regularly observe increased high-sensitivity cardiac troponin (hs-cTn) concentrations in patients with low estimated glomerular filtration rate (eGFR). The challenge is to differentiate acute coronary syndrome (ACS) from increased hs-cTn results across a range of eGFR. The objective of this study was to determined the optimal hs-cTn concentrations for acute myocardial infarction (MI) and a composite cardiovascular outcome across different eGFR ranges and to assess the utility of a low hs-cTn cutoff to rule-out events. METHODS: We undertook an observational study in the emergency department of patients (n = 1212) with symptoms suggestive of ACS who had an eGFR and at least one Roche hs-cTnT and one Abbott hs-cTnI result. The 7-day outcomes were MI or a composite of MI, unstable angina, congestive heart failure, serious ventricular cardiac arrhythmia, or death. The maximum hs-cTn concentration was assessed across different eGFR ranges (<30,30-59,60-89,≥90 ml/min/1.73m2) by spearman correlation, ROC-curve analyses, and sensitivity and negative predictive value (NPV) for the proposed rule-out hs-cTn cutoffs (hs-cTnI<5 ng/l and hs-cTnT<6 ng/l) for the outcomes. RESULTS: Both hs-cTnI and hs-cTnT concentrations were negatively correlated with eGFR. The lower the eGFR, the lower the AUC and the higher the optimal hs-cTn cutoffs for both MI and the composite outcome. The highest combined sensitivity (100%), NPV (100%) and proportion of low-risk for MI (45% of group) was observed for patients with hs-cTnT<6 ng/l with an eGFR≥90. CONCLUSION: The test performance for hs-cTn for diagnosing or ruling-out an acute cardiac event varies per the eGFR. Accurate risk stratification requires knowledge of the eGFR.