External validation, recalibration, and clinical utility of the kidney failure risk equation in patients with advanced CKD: a nationwide retrospective cohort analysis in Peru

Background: The Kidney Failure Risk Equation (KFRE) is widely used for predicting kidney failure, but its external validity in Latin America is limited. A previous study in Peru found that KFRE was miscalibrated but did not evaluate its recalibration or clinical utility. Methods: We conducted a retrospective cohort study using data from EsSalud’s Renal Health Surveillance Program (2013–2022), including 30,031 patients with chronic kidney disease (CKD) stages G3-4. Kidney failure was defined by dialysis initiation or nephrologist-confirmed end-stage renal disease. Calibration was assessed using observed-to-expected (O/E) ratios and differences, calibration slope, and intercept, while discrimination was evaluated using the concordance index (C-index). Recalibrated models were developed, and decision curve analysis (DCA) was performed to evaluate clinical utility. Results: The original KFRE demonstrated good discrimination (C-index: 0.88 at 2 years, 0.85 at 5 years) but poor calibration in-the-large: O/E ratios indicated mean underestimation of risk at 2 years (O/E ratio: 1.84) and a slight mean overestimation at 5 years (O/E ratio: 1.06). Original KFRE also had poor weak (slope: 0.58) and poor moderate calibration. Recalibrated models improved calibration in-the-large, but none achieved good weak (all slope < 1) and moderate calibration. However, DCA showed a higher net benefit for KFRE-based nephrology referrals (in original and recalibrated by method D) compared to Peruvian and international guidelines, especially over a 5-year horizon. Conclusions: Despite miscalibration, KFRE remains valuable for guiding nephrology referrals in Peru, with recalibrated models offering potential improvements. This is the first study in Latin America to rigorously assess the clinical utility of KFRE. Clinical trial number: Not applicable. This study is not a clinical trial.