An evaluation of commonly used surrogate baseline creatinine values to classify AKI during acute infection

Journal article

Introduction Classification of acute kidney injury (AKI) requires a premorbid baseline creatinine, often unavailable in studies in acute infection. Methods We evaluated commonly used surrogate and imputed baseline creatinine values against a “reference” creatinine measured during follow-up in an adult clinical trial cohort. Known AKI incidence (Kidney Disease: Improving Global Outcomes [KDIGO] criteria) was compared with AKI incidence classified by (1) back-calculation using the Modification of Diet in Renal Disease (MDRD) equation with and without a Chinese ethnicity correction coefficient; (2) back-calculation using the Chronic Kidney Disease–Epidemiology Collaboration (CKD-EPI) equation; (3) assigning glomerular filtration rate (GFR) from age and sex-standardized reference tables; and (4) lowest measured creatinine during admission. Back-calculated distributions were performed using GFRs of 75 and 100 ml/min. Results All equations using an assumed GFR of 75 ml/min underestimated AKI incidence by more than 50%. Back-calculation with CKD-EPI and GFR of 100 ml/min most accurately predicted AKI but misclassified all AKI stages and had low levels of agreement with true AKI diagnoses. Back-calculation using MDRD and assumed GFR of 100 ml/min, age and sex-reference GFR values adjusted for good health, and lowest creatinine during admission performed similarly, best predicting AKI incidence (area under the receiver operating characteristic curves [AUC ROCs] of 0.85, 0.87, and 0.85, respectively). MDRD back-calculation using a cohort mean GFR showed low total error (22%) and an AUC ROC of 0.85. Conclusion Current methods for estimating baseline creatinine are large sources of potential error in acute infection studies. Preferred alternatives include MDRD equation back-calculation with a population mean GFR, age- and sex-specific GFR values corrected for “good health,” or lowest measured creatinine. Studies using surrogate baseline creatinine values should report specific methodology.

Authors: Cooper, DJ; Plewes, K; Grigg, MJ; Patel, A; Rajahram, GS

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Elsevier
• Journal: Kidney International Reports
• Volume: 6
• Issue: 3
• Pages: 645-656
• Publication date: 2020-12-31
• Acceptance date: 2020-12-15
• DOI: 10.1016/j.ekir.2020.12.020
• EISSN: 2468-0249
• Pmid: 33732979
• Language: English
• Keywords: sepsis; FFR; acute kidney injury; microbiology