Comparison of seven Dutch emergency departments using standardized mortality ratios in subgroups of patients categorized by presenting complaints; an observational multicenter study

Abstract

Background Comparison of emergency departments (EDs) becomes more important, but differences are difficult to interpret because of the heterogeneity of the ED population regarding reason for ED presentation. The aim of this study was two-fold: First to compare patient characteristics (including diagnoses) across 7 EDs. Secondly, to compare Standardized Mortality Ratios (SMRs) across 7 EDs and in subgroups of ED patients categorized by presenting complaints (PCs). Methods Observational multicenter study including all consecutive visits of 7 EDs. Patient characteristics, including PCs as part of triage systems, and SMRs (observed divided by expected mortality) per ED and for the most common PCs (PC-SMRs) were compared across EDs and presented as funnel plots. The expected mortality was calculated with a prediction model, which was developed using multivariable logistic regression in the overall population and for PCs separately. Demographics, disease severity, diagnoses, proxies for comorbidity and complexity, and PCs (overall population only) were incorporated as covariates. Results We included 693,289 ED visits, of which 1.9% died. Patient characteristics varied markedly among EDs. Expected mortality was similar in prediction models with or without diagnoses as covariate. SMRs differed across EDs, ranging from 0.80 to 1.44. All EDs had SMRs within the 95%-Confidence Intervals of the funnel plot apart from one ED, which had an higher than expected SMR. However, PC-SMRs showed more variation and more EDs had SMRs falling outside the funnel, either higher or lower than expected. The ranking of SMRs across EDs was PC-dependent and differences across EDs are present only for specific PC-SMRs, such as in "dyspnea" and "feeling unwell”. Conclusion In summary, patient characteristics and mortality varied largely across Dutch EDs, and expected mortality across EDs is well assessed in PC subgroups without adjustment for final diagnoses. Differences in SMRs across EDs are PC-dependent. Future studies should investigate reasons of the differences in PC-SMRs across EDs and whether PC-targeted quality improvement programs can improve outcomes.