Evaluation of the safety of the ESC 2011 guidelines for rapid rule-out of NSTEMI using sensitive cardiac troponin I ultra

Abstract

Purpose: Sensitive and high-sensitivity cardiac troponin assays (s-cTn and hscTn) have been shown to improve the early diagnosis of acute myocardial infarction (AMI). The 2011 ESC guidelines for the management of acute coronary syndromes in patients without persistent ST-segment elevation contain for the first time a new fast track rule-out protocol including hs-cTn. It is unknown whether the ESC rule-out protocol can also safely applied using s-cTn assays. This would be of major clinical importance as most hospitals worldwide use s-cTn but not hs-cTn assays. We intended to examine the safety of the ESC fast track rule-out protocol using one specific s-cTnI assay. Methods: In our ongoing international multicenter study 1284 consecutive patients who presented with symptoms suggestive of AMI and did not have significant ST-elevations in the ECG were included. The final diagnosis was adjudicated by two independent cardiologists using all available information including hs-cTnT. The ESC rapid rule-out protocol was tested using a s-cTnI assay (99th percentile at 0.028 μg/l) performed on blood samples obtained in the emergency department at presentation and after 3 hours according to the current guidelines. All patients were divided in line with the ESC algorithm into the subgroups of late presenters with chest pain onset/maximum (CPM) ≥ 6 hours and early presenters with CPM < 6 hours. In the former group, rapid rule-out was based on a single measurement using s-cTnI and in the latter group, on two s-cTnI values, at presentation and at 3 hours. Results: NSTEMI was the final diagnosis in 17% of patients. Overall, 82% of patients (n=1050) had a s-cTnI below the cutoff at presentation. The ESC protocol allowed the rule-out of NSTEMI at presentation in 28% of the total group and after 3 hours in additional 28% of patients. Using only the s-cTnI criteria, the protocol correctly ruled-out 97.7% (95 percent confidence interval (CI) 95.1 to 97.5%) of applicable patients at presentation and 96.7% (95% CI 94.1 to 98.2%) after 3 hours. Adding clinical criteria (pain assessment, GRACE Score, exclusion of differential diagnoses) the protocol correctly ruled-out 99.4% (95% CI 97.7 to 99.9%) at presentation and 98.9% (95% CI 97.0 to 99.6%) after 3 hours. Pain assessment was the key additional criteria. Conclusions: Using a s-cTnI the 2011 ESC guidelines provide an effective way of rapid rule-out of NSTEMI with a very high, however not perfect negative predictive value for rule-out. ClinicalTrials.gov number, NCT00470587.