Point-of-Care Cardiac Markers: Clinical Impact of the Troponin 99~(TH) Percentile Cutoff and Clinical Utility of the Myoglobin Measurement in the Early Management of Chest Pain Patients in a Low to Intermediate Acute Coronary Syndrome Risk Population

摘要

Background: We investigate the influence of myoglobin measurement and the appropriateness of different cardiac troponin I (cTnI) decisional limits on the likelihood of identifying patients with chest pain without ST-segment elevation electrocardiogram in the emergency department (ED). Methods: Five hundred sixteen consecutive patients with non-ST-segment elevation admitted to the hospital were followed up. The first measurement of cardiac markers was performed at point of care in the ED using Stratus CS. Myoglobin and cTnI 99~(TH) percentile reference limits were 86 and 0 03 mug/L, respectively: the coefficient of variation (CV) of cTnI method at this reference limit was 32.3%, whereas the lowest cTnI concentration associated with a CV of 10% or less (International Federation of Clinical Chemistry and Laboratory Medicine recommendations) was 0.07 mug/L. The appropriateness of the admissions in the intensive cardiac unit (cTnI concentration >0.07 mug/L) and nonmonitored beds (cTnI concentration from 0.07 to 0.03 mug/L) was assessed in relation to the final diagnosis of acute myocardial infarction according to the European Society of Cardiology/American College of Cardiology diagnostic criteria: cardiac markers follow-up after hospital admission was performed in central laboratory with cTnI Dimension RxL method (cTnI decisional limit = 0.15 mug/L). Results: Acute myocardial infarction was confirmed in 110 patients (21.3%). The difference between the fraction of patients that was positive in ED, compared with the diagnosis according to European Society of Cardiology/American College of Cardiology criteria, was not statistically significant (P < 0 05) when the cTnI cutoff of 0.03 mug/L was considered. Receiver operating characteristic curve analysis: area under the ROC curve (AUC) for myoglobin = 0.68, 95% confidence interval (CI) = 0.644 to 0.72, P < 0.0001; AUC for cTnI = 0.86, 95% CI = 0.83 to 0.89, P < 0.0001; difference between areas = 0.18, 95% CI = 0.12 to 0.23, P < 0.0001. Conclusions: As previously published, our data confirm that measurement of troponin I with a highly sensitive and specific method makes the measurement of myoglobin unnecessary. Therefore, we suggest that the 99~(TH) percentile reference cutoff for the diagnosis of myocardial infarction in ED could replace the lowest cTnI concentration to meet a 10% CV.