Kidney Week

Abstract: TH-PO1019

GFR Estimation Errors and Association with Outcomes in CKD

Session Information

• CKD: Epidemiology, Risk Factors, and Prevention - 1
  October 24, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: CKD (Non-Dialysis)

• 2301 CKD (Non-Dialysis): Epidemiology, Risk Factors, and Prevention

Authors

• Tio, Maria Clarissa, The University of Mississippi Medical Center, Jackson, Mississippi, United States

Maria Clarissa Tio, MD, MPH, FASN

• Zhu, Xiaoqian, The University of Mississippi Medical Center, Jackson, Mississippi, United States

Xiaoqian Zhu, PhD

• Obi, Yoshitsugu, The University of Mississippi Medical Center, Jackson, Mississippi, United States

Yoshitsugu Obi, MD, PhD, FASN

• Yen, Timothy E., The University of Mississippi Medical Center, Jackson, Mississippi, United States

Timothy E. Yen, MD

• Hall, Michael E., The University of Mississippi Medical Center, Jackson, Mississippi, United States

Michael E. Hall, MD, MS

• Dossabhoy, Neville R., The University of Mississippi Medical Center, Jackson, Mississippi, United States

Neville R. Dossabhoy, MD, FASN

• Shafi, Tariq, Houston Methodist, Houston, Texas, United States

Tariq Shafi, MBBS, MHS, FASN

Background

Estimated GFR (eGFR) can often be significantly different from measured (mGFR). The clinical implications of large errors in eGFR on risks of outcomes in CKD are unknown.

Methods

Using the Chronic Renal Insufficiency Cohort, a multi-center, prospective cohort of persons with CKD, we analyzed 1,423 participants with mGFR (urinary clearance of iothalamate). We calculated eGFR using the CKD-EPI 2021 creatinine equation. We defined large errors as eGFR that was 15% higher or lower than mGFR. We evaluated the association of large errors, compared to no errors, with outcomes using Fine-Gray subdistribution hazard models for kidney failure with death as a competing risk and Cox proportional hazards models for death, and first occurrence of hyperkalemia, hyperphosphatemia, and anemia. All models were adjusted for age, sex, and race/ethnicity. Data were provided by NIDDK CR, a program of the NIDDK.

Results

Mean age was 56 years, 44% were women, and 37% were Black participants. 776 (55%) participants had large errors: 428 (30%) had mGFR > eGFR and 242 (17%) had mGFR < eGFR. Those with mGFR < eGFR tended to be of White or Hispanic race/ethnicity, have diabetes, and have a higher systolic blood pressure and body mass index. mGFR > eGFR (underestimation) was associated with lower risk of death (HR=0.73; 95%CI: 0.65-0.82), hyperphosphatemia (HR=0.68; 95%CI: 0.49-0.94), and anemia (HR=0.84; 95%CI: 0.73-0.97), with trends toward lower risk of kidney failure and hyperkalemia (Table 1). Conversely, mGFR < eGFR (overestimation) was associated with increased risk of kidney failure (HR=1.22; 95%CI: 1.11-1.35) and anemia (HR=1.39; 95%CI: 1.16-1.66), with trends toward increased risk of death, hyperkalemia, and hyperphosphatemia (Table). Every 10 mL/min/1.73 m² increase in bias (eGFR-mGFR) was significantly associated with an increased 22% risk of death, 19% risk of kidney failure, 20% risk of hyperkalemia, 18% risk of hyperphosphatemia, and 18% risk of anemia (Table).

Conclusion

Among persons with CKD who have large differences between mGFR and eGFR, risks of adverse outcomes track closer to mGFR than eGFR.

Funding

• Other NIH Support