Analysis of comorbidity in an emergency department using diagnostic coding: The Elixhauser Index

OBJECTIVE: To analyze the comorbidity of patients attending an emergency department (ED) using the Elixhauser Index (EI) and examine its association with the length of stay and discharge destination. METHODS: We conducted aetrospective observational study based on the Emergency Department Minimum Basic Dataset for 2019, 2022, and 2023, excluding pandemic years. Diagnoses were coded using International Classification of Diseases-version-10 Clinical Modification (ICD-10-CM), and the EI was applied to assess comorbidity. Associations between comorbidity, length of stay (< 16 hours vs $ 16 hours), and discharge destination were analyzed. RESULTS: More than 12% of patients had at least 1 comorbidity (EI $ 1). Among episodes < 16 hours, 92% showed no comorbidity, whereas among episodes $ 16 hours, nearly 50% had EI $ 1 (P < .001). Among patients admitted to the tertiary referral center, fewer than 7% had moderate or severe comorbidity (EI $ 2). Patients with greater comorbidity were referred to lower-complexity facilities or to hospital-at-home programs. CONCLUSIONS: The EI allows characterization of the heterogeneity of the ED population. The organizational model of Hospital de la Santa Creu i Sant Pau, oriented toward geriatric and network-based care, facilitates referral of complex patients to more appropriate resources, reducing admissions to high-technology hospitals. Incorporating comorbidity analysis may improve ED planning and funding.