Key result
Sensitive troponin I limit of detection rules out acute myocardial infarction with ~94% sensitivity.
Why the study?
It is uncertain whether acute myocardial infarction can be excluded with a single blood test on arrival using a contemporary sensitive troponin I assay that is not high-sensitivity.
Does a single contemporary sensitive troponin I assay below the limit of detection safely rule out acute myocardial infarction in patients presenting to the emergency department with suspected cardiac chest pain?
Cohort (n=414)
Does a single contemporary sensitive troponin I assay below the limit of detection safely rule out acute myocardial infarction in patients presenting to the emergency department with suspected cardiac chest pain?
A single contemporary sensitive troponin I assay below the limit of detection on arrival is insufficient to safely rule out acute myocardial infarction without serial sampling or additional clinical information.
Answers are grounded in this paper and cite their sources.
Contemporary troponin assays at LoD may not safely exclude AMI on single testing; leaves open whether optimized thresholds extend early rule-out.
OBJECTIVE: With a high-sensitivity troponin assay, it may be possible to exclude acute myocardial infarction with a single blood test on arrival in the emergency department by using a novel 'rule out' cut-off set at the limit of detection of the assay. We aimed to determine whether this can also be achieved using a contemporary sensitive troponin assay that does not meet 'high-sensitivity' criteria. METHODS: In a prospective diagnostic cohort study, we included patients presenting to the emergency department with suspected cardiac chest pain. For this secondary analysis, serum samples drawn on arrival were tested using a contemporary sensitive troponin I assay (s-cTnI; Siemens Ultra ADVIA Centaur, 99th percentile 40 ng/L, limit of detection 6 ng/L). Acute myocardial infarction was adjudicated by two independent investigators based on reference standard troponin testing ≥12 h after symptom onset. RESULTS: Of 414 participants, 70 (16.9%) had acute myocardial infarction and 205 (49.5%) had initial s-cTnI concentrations below the limit of detection. Using the limit of detection as a 'rule out' cut-off gave a sensitivity of 94.3% (95% CI 86.0-98.4%) for acute myocardial infarction. If only patients with s-cTnI below the limit of detection and no electrocardiogram ischaemia were considered to have acute myocardial infarction 'ruled out' (41.8% of the cohort, n = 174), sensitivity would rise to 97.1% (90.1-99.7%) and negative predictive value to 98.8% (95.9-99.9%). CONCLUSIONS: Acute myocardial infarction cannot be excluded in patients with s-cTnI concentrations below the limit of detection using the contemporary sensitive assay evaluated. Future work with this assay should focus on serial sampling over 1-3 h and combination with clinical information and/or additional biomarkers.
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Body et al. (2015) conducted a cohort in Suspected cardiac chest pain (n=414). Contemporary sensitive troponin I assay (s-cTnI) vs. Reference standard troponin testing ≥12 h after symptom onset was evaluated on Acute myocardial infarction (Sensitivity 94.3%, 95% CI 86.0-98.4). Using a contemporary sensitive troponin I assay limit of detection as a rule-out cut-off yielded a sensitivity of 94.3% for acute myocardial infarction.
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