Scientific Poster Session I - Original Research

Original Research
  Saturday, October 12, 2024
  11:30 AM–01:00 PM

Abstract

Introduction:

The 2021 Chronic Kidney Disease-Epidemiology (CKD-EPIcr 2021) equation is preferred for estimated glomerular filtration rate (eGFR). Currently, eGFR values are reported as indexed values (eGFR in mL/min/1.73 m²); however, eGFR adjusted for body surface area (eGFR_BSA in mL/min) should be used for drug dosing, an important concept for pharmacists more familiar with the Cockcroft-Gault (CG) equation. There is a need to evaluate variation in kidney function estimates when applied for drug dosing in obese patients.

Research Question or Hypothesis:

What are the differences in kidney function estimates using CKD-EPIcr 2021 and CG equations in obese individuals and implications for drug dosing?

Study Design:

Retrospective review of adult patients at Methodist LeBonheur Healthcare May-July 2023.

Methods:

Patients with body mass index (BMI) >30 kg/m², eGFR <60 mL/min/1.73 m², and stable kidney function were included. Mean differences in indexed eGFR and eGFR_BSA, differences with CG estimates [with adjusted body weight (AdjBW) and total body weight (TBW)], and the percent of estimates within common drug dosing thresholds (15-29, 30-44, 45-60, >60 mL/min) were evaluated.

Results:

400 patients were included: mean age 67±12 years, BMI 38±8 kg/m2, 65% female. Mean indexed eGFR and eGFR_BSA were 43±11 and 56±16, respectively; [mean difference 13 (95% CI: 12-14)]. The difference was greater in patients with BMI =40 kg/m² compared with BMI <40 kg/m² (20 vs 10, p<0.001). Mean differences between eGFR_BSA and CG-TBW and CG-AdjBW estimates were 11 (56 vs 67, 95% CI:10-13) and 6 (56 vs 50, 95% CI:5-7), respectively. Use of indexed eGFR placed 70% more patients in a lower dosing category compared to eGFR_BSA while CG-TBW placed 29% in a higher category.

Conclusion:

In obese patients, use of indexed eGFR may result in underestimation of kidney function for drug dosing, with increased effect as BMI increases. Pharmacists must understand the potential clinical implications of failure to use eGFR_BSA in obese patients.

Presenting Author

Samuel Greer PharmD
Methodist University Hospital

Authors

Joyce Broyles PharmD, BCNSP, DPLA
B. Tate Cutshall PharmD
Methodist Le Bonheur Healthcare

Kori Holman PharmD
Methodist University Hospital

Joanna Hudson PharmD
The University of Tennessee