Case–control study to investigate variables associated with incidents and adverse events in the emergency department

Objective To detect and analyse incidents (Is) and adverse events ( AEs ) in the ED . We hypothesised that I/ AE are associated with patient load. Methods We undertook a case–control study in a tertiary level hospital ED (from 1 April 2012 to 31 March 2013). Three percent of patients were randomly selected and screened for I/ AEs . I/ AEs were adjudicated by consensus of four FACEMs . Controls were matched to cases 2:1. Logistic regression was used to analyse the data. Results We sampled 2167 patients. After exclusions, 217 I/ AEs were detected and analysed. The I and AE rates were 6.0 and 4.1%, respectively. The serious AE rate was 0.8% and 30 day mortality was 0.1%. Diagnostic error occurred in 3.7% of all patients and adverse drug reactions in 2.5%. Seventy‐seven percent of the I/ AEs were judged preventable. ED occupancy of <35 patients was the reference group. Compared with this group, if 36–40 or 41–45 patients were in the ED , I/ AEs were more likely to occur ( odds ratio [OR] 2.37 [95% confidence interval ( CI ) 1.40–4.01, P  < 0.0] and 1.8 [95% CI 1.03–3.15, P  = 0.04], respectively) but not when there were >46 patients ( OR 1.7, 95% CI 1.0–3.1). Higher hospital occupancy (90–99%) was a protective factor for sustaining an I/ AE ( OR 0.57, 95% CI 0.35–0.92, P  = 0.02). Conclusion I/ AEs are common in the ED and a large proportion is preventable. Strategies for prevention are required. The relationship with patient load needs further clarification, since our data suggests increased I/ AE rates with higher occupancy but not highest occupancy.