Acute Kidney Injury Diagnostic Accuracy and Implications of Different Baseline Creatinine Equations.

Introduction: Acute kidney injury (AKI) definitions rely on known baseline serum creatinine (Crb), unavailable in up to 75% of hospitalized children. New equations (the AKI Baseline Creatinine [ABC] methods) for estimating Crb were derived from children without kidney disease. We aimed to externally validate ABC methods in an international cohort and assess how different Crb equations alter AKI epidemiology. Methods: AWARE was a prospective international study of critically ill children (aged 0-25 years) from 32 pediatric intensive care units (ICUs). A subset of AWARE (n = 2451) with known Crb (gold standard) was used to validate ABC methods using statistical measures of precision (R2) and accuracy (within 10% or 30% of gold standard). The entire cohort (N = 4984) was used to determine how different Crb estimating equations (3 ABC equations and 4 published estimated glomerular filtration rate [eGFR] equations imputing Crb) impact AKI incidence and its association with key clinical outcomes, including 28-day mortality, using univariate and multivariate analysis. Results: The ABC-Age equation (requiring only age) demonstrated similar accuracy and precision compared with existing Crb equations. The ABC-Creatinine equation (includes age and hospital creatinine value) outperformed existing Crb equations by up to 15% in precision (ABC-Creatinine, R2 = 0.51 vs. full-age spectrum [FAS], R2 = 0.36) and 32% in accuracy (ABC-Creatinine, 66% vs. original Schwartz, 34%). For the entire cohort, AKI incidence varied from 7% to 12%, depending on Crb definition. ABC equations were associated with clinical outcomes similarly to existing Crb equations. Conclusion: ABC-Creatinine equation (with minimal variables) outperformed existing Crb equations for accuracy and precision as the optimal method for Crb estimation. Crb definition variability alters AKI incidence and epidemiology, necessitating standardization.