Association of UACR and UPCR with kidney failure: analysis of observational data in children with chronic kidney disease.

BACKGROUND

Urinary albumin-to-creatinine ratio (UACR) and protein-to-creatinine ratio (UPCR) are established markers for risk stratification in pediatric chronic kidney disease (CKD), yet their relative strength of association with CKD progression remains unclear. We compared a head-to-head evaluation of UACR and UPCR associations with estimated glomerular filtration rate (eGFR) decline and kidney survival in a large pediatric CKD cohort.

METHODS

We analyzed 596 children aged 6-17 years with CKD stages 3-4 from the 4C cohort. Baseline UACR and UPCR were log-transformed and z-standardized. CKD progression was evaluated by annual eGFR slope and a composite kidney outcome (50% eGFR loss, eGFR <10 mL/min/1.73 m² or kidney replacement therapy). Associations per 1-SD increase were estimated using adjusted linear mixed-effect and Cox models. Differences in effect sizes were assessed using bootstrap-based bias-corrected and accelerated 95% confidence intervals (CI).

RESULTS

Mean (SD) age was 12.4 (3.3) years; 70% had congenital anomalies of the kidneys and urinary tract (CAKUT). Median (interquartile range) eGFR was 28 (14) mL/min/1.73 m². Over a median follow-up of 2.5 (3.8) years, 334 events occurred. A 1-SD increase in log-UACR and log-UPCR was associated a 2.17-fold (95% CI 1.84 to 2.55) and 1.70-fold (95% CI 1.52 to 1.90) higher risk of the composite outcome, respectively; UACR showed a 28% stronger association (HRUACR/HRUPCR = 1.28; 95% CI 1.12 to 1.53). No relative difference was found in overall eGFR slope change (slope ∆UACR - slope ∆UPCR = -0.05; 95% CI -0.50 to 0.24), but UACR showed stronger associations in children with advanced CKD and severe proteinuria.

CONCLUSION

Both UACR and UPCR were independently associated with CKD progression in this pediatirc cohort. In direct comparison, UACR demonstrated stronger associations with adverse kidney outcomes, suggesting a comparatively greater prognostic signal and supporting current guideline emphasis on albuminuria for risk stratification and intervention outcome monitoring.