Rhabdo-RRT score: development and external validation of an emergency department tool for predicting renal replacement therapy in rhabdomyolysis

Background Early identification of patients with rhabdomyolysis who will require renal replacement therapy (RRT) remains challenging in the emergency department (ED). A simple ED-applicable tool focused on RRT risk may improve early risk stratification. Methods This retrospective two-centre cohort study included adults presenting to the ED with rhabdomyolysis between February 2019 and September 2025. Ankara Bilkent City Hospital served as the derivation cohort and Ankara Etlik City Hospital as the external validation cohort. The primary outcome was in-hospital RRT requirement. Independent predictors were identified by multivariable logistic regression, converted into a weighted point-based score and applied unchanged to the validation cohort without recalibration or modification. Results A total of 701 patients were included: 485 in the derivation cohort and 216 in the validation cohort. RRT was required in 133 patients (19.0%), including 79 (16.3%) and 54 (25.0%) patients in the derivation and validation cohorts, respectively. The Rhabdo-RRT Score ranged from 0 to 13 points and included age, admission creatine kinase, serum albumin and rhabdomyolysis aetiology. Discrimination was strong, with an area under the curve of 0.946 (95% CI 0.914 to 0.977) in the derivation cohort and 0.862 (95% CI 0.802 to 0.922) in the validation cohort. With scores of 0–4 defining the low-risk category, the corresponding negative predictive value was 98.4% (95% CI 96.1% to 99.4%) in the derivation cohort and 94.7% (95% CI 88.3% to 97.7%) in the validation cohort. At the ≥9-point high-risk threshold, specificity was 98.3% (95% CI 96.5% to 99.2%) and 95.7% (95% CI 91.4% to 97.9%), and positive predictive value was 89.4% (95% CI 79.7% to 94.8%) and 79.4% (95% CI 63.2% to 89.7%) in the derivation and validation cohorts, respectively. Conclusions The Rhabdo-RRT Score is a simple admission-based tool for estimating RRT risk in ED patients with rhabdomyolysis. External validation supports its potential use for early risk stratification and RRT resource planning in acute care.