Ascertainment and epidemiology of acute kidney injury varies with definition interpretation

Background and objectives: Differences in defining acute kidney injury (AKI) may impact incidence ascertainment. We assessed the effects of different AKI definition interpretation methods on epidemiology ascertainment. Design, setting, participants, & measurements: Two groups were studied at Texas Children's Hospital, Houston, Texas: 150 critically ill children (prospective) and 254 noncritically ill, hospitalized children receiving aminoglycosides (retrospective). SCr was collected for 14 d in the prospective study and 21 d in the retrospective study. Children with known baseline serum creatinine (bSCr) were classified by the pediatric Risk, Injury, Failure, Loss, End-Stage Kidney Disease (pRIFLE) AKI definition using SCr change (pRIFLE_ΔSCr), estimated creatinine clearance (eCCl) change (pRIFLE_ΔCCl), and the Acute Kidney Injury Network (AKIN) definition. In subjects without known bSCr, bSCR was estimated as eCCl = 100 (eCCl₁₀₀) and 120 ml/min per 1.73 m² (eCCl₁₂₀), admission SCr (AdmSCr) and lower/upper normative values (NormsMin, NormsMax). The differential impact of each AKI definition interpretation on incidence estimation and severity distribution was evaluated. Results: pRIFLE_ΔSCr and AKIN led to identical AKI distributions. pRIFLE_ΔCCl resulted in 14.5% (critically ill) and 11% (noncritical) more patients diagnosed with AKI compared to other methods (P 0.05). Different bSCr estimates led to differences in AKI incidence, from 12% (AdmSCr) to 87.8% (NormsMin) (P 0.05) in the critically ill group and from 4.6% (eCCl₁₀₀) to 43.1% (NormsMin) (P 0.05) in the noncritical group. Conclusions: AKI definition variation causes interstudy heterogeneity. AKI definition should be standardized so that results can be compared across studies.