A method to estimate expected day-surgery activity in hospitals of the Spanish National Health System

Methods Data source: Minimum Basic Data Set (MBDS) of hospital care episodes. Potential Day Surgery Episode (PDSE) was defined as the hospital episode with a surgical procedure (ICD-9-CM), programmed admission and home discharge. To be considered as PDSE, the selected procedure must appear in at least 50 day-surgery cases and be developed in at least 5 hospitals. The study database included: MBDS of 188 (85%) hospitals in the National Health System and 32 (15%) Spanish private hospitals in the year 2006 with 1,162,082 surgical admissions. From 1,770 procedures identified (ICD-9-MC), 798 fulfilled PDSE criteria that were finally grouped in 204 procedure groups. From the total number of surgical admissions, 931,630 episodes were considered as PDSE and 541,715 were observed as real day-surgery episodes (substitution index of 58.1%). A logistic regression model was applied to estimate the expected number of day-surgery episodes. The dependent variable was day-surgery case (yes/no).