Background Older adults are the most frequent users of emergency services, accounting for up to a quarter of all emergency department (ED) attendances. In addition, older adults require more healthcare resources, experience longer ED stays and demonstrate higher rates of adverse outcomes following emergency care such as return to ED, emergency hospitalisation and death. The aim of this study is to perform a systematic review and meta-analysis of validation studies of the ISAR to determine its predictive value in identifying older adults at risk of adverse outcomes within 30, 90 or 180 days after ED or hospital discharge.

Methods A systematic literature search was conducted to identify studies validating the ISAR rule in adults aged ≥65 years attending the ED. The methodological quality of selected studies was assessed by two independent reviewers using the quality of diagnostic accuracy studies tool (QUADAS-2). A score of ≥2 was used to identify high risk patients. A bivariate random effects model was applied to generate pooled summary estimates of sensitivity and specificity. Heterogeneity was assessed graphically using summary receiver-operating characteristic (ROC) graphs and statistically using the variance of the logit transformed sensitivity and specificity.

Results Thirty studies including 23 unique patient cohorts are included. The methodological quality of the studies is varied, particularly regarding blinding of outcome assessors. A total of 11,334 patients are included in the meta-analysis. At a cut-off of ≥2, the pooled sensitivity of the ISAR rule for predicting ED return, hospitalisation and mortality at 6 months is 0.84 (95% CI 0.73–0.91), 0.84 (95% CI 0.76–0.90) and 0.89 (95% CI 0.79–0.95) respectively, with a pooled specificity of 0.28 (95% CI 0.22–0.36), 0.28 (95% CI 0.22–0.35) and 0.33 (95% CI 0.24–0.45). Similar values are demonstrated for these outcomes at 30 and 90 days. There is little heterogeneity across studies.

Discussion The ISAR screening tool demonstrates high pooled estimates of sensitivity across all outcomes and time-points, indicating that it can be used to rule out adverse events in older adults who are deemed low risk (<2 points) in the clinical setting. The low levels of heterogeneity gives us confidence that the pooled estimates reflect the predictive ability of the ISAR rule in clinical practice. The ISAR is a useful tool for clinicians in deciding which older patients can be safely discharged from the ED.