Accuracy of etiological classification of out-ofhospital cardiac arrest: A scoping review

Introduction : The Utstein reporting template classifies the etiology of OHCA into "presumed cardiac" and "obvious non-cardiac" or "medical" and "non-medical" categories; however, the accuracy of these classifications is unclear. Ascertaining more accurately the etiology of OHCA is important to tailor advanced life support and identify etiologically consistent patient cohorts for reporting incidence and outcome and enrollment in clinical trials. This scoping review was proposed to identify the state of agreement on etiological classification based on emergency medical service (EMS) data using the Utstein format against other sources. Method : We searched Medline, EBM-Cochrane, and Embase databases from 1946-2023 to identify studies that reported initial and confirmed etiologies of OHCA. A descriptive review of the included studies was conducted. Result : The search yielded 22,994 citations. After excluding duplicates, 16,932 citations were reviewed for titles and abstracts. Twelve studies met the inclusion criteria of this review. The frequency of presumed cardiac etiologies based on EMS data was higher than confirmed cardiac etiologies (88% vs 33%) with 83-94% sensitivity and 73-76% specificity. In contrast, the frequency of presumed non-cardiac etiologies was lower than confirmed non-cardiac etiologies (3% vs 27%) with 52-74% sensitivity and 90-97.7% specificity estimated for respiratory disease. Conclusion : Major disparities exist between current etiological classifications based on the Utstein reporting template and robust sources such as autopsy and medical records. Data linkage and validation are necessary to confirm the etiology of OHCA. Further research is needed on how this misclassification affects reported incidence and outcomes, and how contributing factors may improve etiological classifications.