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Abstract: PO1925

Performance of Creatinine-Based Equations to Estimate Glomerular Filtration Rate in the Context of Drug Dosage Adaptation

Session Information

Category: Pathology and Lab Medicine

  • 1600 Pathology and Lab Medicine

Authors

  • Delanaye, Pierre, CHU de Liege - Hopital du Sart Tilman, Liege, Liège, Belgium
  • Björk, Jonas, Skanes universitetssjukhus Lund, Lund, Skåne, Sweden
  • Pottel, Hans, KULAK, Kortrijk, Belgium
  • Nyman, Ulf, Skanes universitetssjukhus Lund, Lund, Skåne, Sweden

Group or Team Name

  • European Kidney Function Consortium
Background

The 1976 Cockcroft-Gault (CG) creatinine-based equation is still used to estimate GFR (eGFR) for dose adaptation of drugs excreted by glomerular filtration although it estimates creatinine clearance. It was developed based on non-standardized creatinine assays and is not recommended by any nephrology guidelines. Incorrect eGFR may lead to hazardous over- or underdosing. We aimed to compare the performance of CG with modern equations based on standardized creatinine assays.

Methods

In a cross-sectional analysis CG was validated against measured GFR (mGFR; using various tracer methods) in 15,479 participants and compared with the Modification-of-Diet-in-Renal-Diseases (MDRD), Chronic-Kidney-Disease-Epidemiology (CKD-EPI), Lund-Malmö-Revised (LMR), and European-Kidney-Function-Consortium (EKFC) equations. Validation focused on bias, imprecision and accuracy (percentage of estimates within ±30% of mGFR, P30), overall and stratified for mGFR, age and body mass index intervals at mGFR <60 mL/min, as well as classification in mGFR stages.

Results

The CG equation performed worse than the other equations, overall and in mGFR, age and BMI subgroups in terms of bias (systematic overestimation), imprecision and accuracy (P30 overall for CG/MDRD/CKD-EPI/LMR/EKFC 73.6%/81.0%/82.4%/87.5%/86.9%) except for patients ≥65 years where bias and P30 were similar to MDRD and CKD-EPI, but worse than LMR and EKFC. At BMI [18.5-25[kg/m2, all equations performed similarly and at BMI<18.5kg/m2 CG and LMR had the best results though all equations had poor P30-accuracy (CG/LMR 58.7%/57.2%). At BMI≥25kg/m2, bias of CG increased with increasing BMI (+19.3mL/min at BMI≥40kg/m2). The four more recent equations also classified mGFR stages better than CG.

Conclusion

The CG equation exhibited worse performance to estimate GFR overall and in analyses stratified for GFR, age, and BMI. CG was inferior to correctly classify the patients in the mGFR staging compared to more recent creatinine-based equations.