A bedside equation to estimate 24‑h proteinuria in children with nephrotic syndrome: Derivation and temporal validation

To date, 24-h urine protein (24hUP) excretion remains the gold standard for quantifying proteinuria and is a strong predictor of renal outcomes in glomerular diseases.Although current guidelines allow nephrotic-range proteinuria to be diagnosed using either single-void urine protein-creatinine ratio (UPCR) or 24hUP thresholds, these cut-offs primarily confirm disease presence and provide limited quantitative guidance for clinical decision-making during the acute phase of pediatric primary nephrotic syndrome (PNS).The present study thus aimed to provide a method with which to estimate 24hUP in children with PNS.A total of 251 children with PNS were included and divided into a derivation cohort (n=171) and an independent validation cohort (n=80).Log-log linear regression models were constructed using UPCR adjusted by estimated 24-h creatinine excretion derived from the Cockcroft-Gault, Hellerstein and Ghazali-Barratt equations, with age and sex incorporated as covariates.Model performance was assessed using coefficients of determination (R 2 ), root mean square error (RMSE), mean absolute error (MAE) and calibration analyses.The optimal model, based on Cockcroft-Gault-adjusted UPCR, demonstrated good predictive performance in external validation (RMSE, 11.39 mg/m 2 /h; MAE, 9.26 mg/m 2 /h; R 2 , 0.91), with 93.8 and 96.3% of estimates within 20 and 30% of observed 24hUP values, respectively.The application of the model indicated that a substantial proportion of children could safely avoid immediate 24-h urine collection without missing cases of marked proteinuria.On the whole, a bedside equation using adjusted UPCR may serve as a practical surrogate for estimating 24hUP in children with PNS and facilitate clinical decision-making in routine practice.