Indeterminate zone high-sensitivity troponin levels in a rapid acute myocardial infarction assessment algorithm and patient dispositions

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Conference Proceeding

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Academic emergency medicine


Background and Objectives: The multicenter High Sensitivity Cardiac Troponin I (hs-cTnI) in the United States (HIGH-US) study reported a 1-hour Emergency Department (ED) hs-cTnI algorithm for the assessment of acute myocardial infarction (AMI). However, 783 (37.1%) patients were placed in the algorithm's indeterminate zone, not meeting the rule-out or rule-in criteria. Our objectives were to describe the AMI and 30-day AMI/death rates and clinical characteristics of these patients placed in observation/inpatient beds (OBS/ADM) compared to having an ED discharge (EDD).

Methods: In this prospective cohort study 2113 consenting adults with any symptoms suspicious for AMI were enrolled from 2015-2016 in 29 US medical centers. There were no patient exclusion criteria. Baseline and 1-hour plasma samples were analyzed using the Siemens Atellica hs-cTnI assay (99th % = 47.0 ng/L), with results not available to the treating physician. AMI diagnosis was independently adjudicated using local contemporary troponin assays and all 30-day clinical data available. Patients were placed in OBS/ADM or had EDD according to each site's clinical practice. Stepwise logistic regression modeling was used to determine which of 25 clinical patient characteristics were associated with OBS/ADM disposition decisions.

Results: Of 763 (30.3%) of the intermediate zone placed patients with complete data available, 532 (69.7 %) were placed in OBS/ ADM and 231 (30.3%) had an EDD. Adjudicated AMI rates and 30-day AMI/death rates were different in these 2 groups (41 [7.7%], 2 [0.9%], p = 0.001 and 15 [2.8%], 1 [0.4%] respectively, p = 0.050). The clinical variables associated with OBS/ADM placement were age, hypertension, eGFR < 60, abnormal ECG, and previous revascularization (odds ratio estimates of 1.027, 1.764, 1.955, 1.700 and 1.620 respectively). The OBS/ADM to EDD ratios varied widely amongst the participating centers (100.0-50.0%).

Conclusion: The correct disposition decision for patients not ruling out or ruling in for AMI using a 1-hour hs-cTnI algorithm remains unclear. ED physicians, using contemporary troponin assays and clinical evaluations for 231 patients with EDD but who were placed in the hs-cTnI algorithm intermediate zone, missed 1 (0.4%) AMI, with 15 (2.8%) patients having 30-day AMI/death. The absence of our reported cardiac risk factors likely contributed to the EDD decision. Further studies are needed to validate our results.




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