The effect of low-complexity patients on emergency department waiting times

Study objective: The extent to which patients presenting to emergency departments (EDs) with minor conditions contribute to delays and crowding is controversial. To test this question, we study the effect of low-complexity ED patients on the waiting times of other patients. Methods: We obtained administrative records on all ED visits to Ontario hospitals from April 2002 to March 2003. For each ED, we determined the association between the number of new low-complexity patients (defined as ambulatory arrival, low-acuity triage level, and discharged) presenting in each 8-hour interval and the mean ED length of stay and time to first physician contact for medium- and high-complexity patients. Covariates were the number of new high- and medium-complexity patients, mean patient age, sex distribution, hospital teaching status, work shift, weekday/weekend, and total patient-hours. Autoregression modeling was used given correlation in the data. Results: One thousand ninety-five consecutive 8-hour intervals at 110 EDs were analyzed; 4.1 million patient visits occurred, 50.8% of patients were women, and mean age was 38.4 years. Low-, medium-, and high-complexity patients represented 50.9%, 37.1%, and 12% of all patients, respectively. Mean (median) ED length of stay was 6.3 (4.7), 3.9 (2.8), and 2.2 (1.6) hours for high-, medium-, and low-complexity patients, respectively, and mean (median) time to first physician contact was 1.1 (0.7), 1.3 (0.9), and 1.1 (0.8) hours. In adjusted analyses, every 10 low-complexity patients arriving per 8 hours was associated with a 5.4-minute (95% confidence interval [CI] 4.2 to 6.0 minutes) increase in mean length of stay and a 2.1-minute (95% Cl 1.8 to 2.4 minutes) increase in mean time to first physician contact for medium- and high-complexity patients. Results were similar regardless of ED volume and teaching status. Conclusion: Low-complexity ED patients are associated with a negligible increase in ED length of stay and time to first physician contact for other ED patients. Reducing the number of low-complexity ED patients is unlikely to reduce waiting times for other patients or lessen crowding.