A-041 Clinical Performance and Risk Classification Agreement of Point-of-Care i-STAT High-Sensitivity Troponin I Compared with Abbott Alinity hs-cTnI in ED Patients with Suspected Acute Coronary Syndrome

Abstract

Point-of-care (POC) high-sensitivity cardiac troponin testing in the emergency department (ED) can streamline triage and reduce length of stay by improving turnaround time and accelerating clinical decision-making, particularly for low-risk patients. However, these efficiency gains must be balanced with diagnostic safety. In this study, we evaluated the clinical performance of the recently FDA-cleared i-STAT high-sensitivity troponin I (hs-cTnI) assay for risk classification of patients presenting to the ED with suspected acute coronary syndrome (ACS), using the accelerated ED hs-cTnI protocol currently implemented at our institution. We hypothesized that the i-STAT hs-cTnI assay would demonstrate high agreement with Abbott Alinity hs-cTnI for ED risk stratification, with acceptable diagnostic safety for identification of low-risk patients. Paired testing was performed on the same lithium heparin specimens (n = 269) obtained from 238 patients, with i-STAT analysis conducted first using whole blood, followed by Abbott Alinity testing on plasma. Demographic and clinical data were retrospectively extracted from electronic medical records. Final diagnosis and clinical risk adjudication were independently performed by two emergency physicians based on clinical data and Abbott Alinity hs-cTnI results, which served as the institutional reference standard. Risk categorization based strictly on troponin results from both methods (low <5 ng/L; intermediate 5 ng/L to the 99th percentile, sex-specific; high > 99th percentile) was compared with clinician risk classifications. For patients (87%) with only a single specimen available (0 hr.), a high-risk classification based on troponin results was considered consistent with chronic myocardial injury if documented as such by at least one adjudicating clinician, regardless of the assigned risk level. For patients with two specimens available (0 hr. and 2hr.), both cutoffs and deltas were applied according to the ED troponin protocol to determine risk stratification. Overall agreement in troponin-based risk classification between i-STAT and Abbott Alinity was 83%. Among discordant cases (17%), the majority (90%) were classified as intermediate risk by i-STAT, while only one case (2%) was classified as low risk. Agreement with clinical adjudication was significantly higher for Abbott Alinity compared with i-STAT (86% vs 71%; p=0.0002). Importantly, all patients ultimately diagnosed with myocardial infarction (n=7) were classified identically by both assays and clinical adjudication, with none misclassified as low risk. The i-STAT hs-cTnI assay demonstrated high agreement with the Abbott Alinity platform for troponin-based risk classification and correctly identified all myocardial infarction cases. Although overall agreement with clinical adjudication was lower than that of the Abbott Alinity assay, the very low rate of low-risk misclassification suggests that the i-STAT assay may be safely used for early risk stratification of ED patients, particularly for identifying low-risk populations.