Does the definition of preventable emergency department visit matter? An empirical analysis using 20 million visits in Ontario and Alberta

Objectives This study had two objectives: (1) to estimate the prevalence of preventable emergency department (ED) visits during the 2016-2020 time period among those living in 19 large urban centers in Alberta and Ontario, Canada, and (2) to assess if the definition of preventable ED visits matters in estimating the prevalence. Methods A retrospective, population-based study of ED visits that were reported to the National Ambulatory Care Reporting System from April 1, 2016, to March 31, 2020, was conducted. Preventable ED visits were operationalized based on the following approaches: (1) Canadian Triage and Acuity Scale (CTAS), (2) ambulatory care-sensitive conditions (ACSC), (3) family practice-sensitive conditions (FPSC), and (4) sentinel nonurgent conditions (SNC). The overall proportion of ED visits that were preventable was estimated. We also estimated the adjusted relative risks of preventable ED visits by patients' sex and age, fiscal year, province of residence, and census metropolitan area (CMA) of residence. Results There were 20,171,319 ED visits made by 8,919,618 patients ages 1 to 74 who resided in one of the 19 CMAs in Alberta or Ontario. On average, there were 2.26 visits per patient over the period of 4 fiscal years; most patients made one (44.22%) or two ED visits (20.72%). The overall unadjusted prevalence of preventable ED visits varied by definition; 35.33% of ED visits were defined as preventable based on CTAS, 12.88% based on FPSC, 3.41% based on SNC, and 2.33% based on ACSC. Conclusions There is a substantial level of variation in prevalence estimates across definitions of preventable ED visits, and care should be taken when interpreting these estimates as each has a different meaning and may lead to different conclusions. The conceptualization and measurement of preventable ED visits is complex and multifaceted and may not be adequately captured by a single definition.