Kidney Week

Abstract: SA-OR33

Performance of Creatinine-Based GFR Estimating Equations in Young Adults

Session Information

• Epidemiology of CKD Progression: Who, Why, and When?
  November 04, 2023 | Location: Room 119, Pennsylvania Convention Center
  Abstract Time: 05:15 PM - 05:24 PM

Category: CKD (Non-Dialysis)

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

Author

• Inker, Lesley Ann, Tufts Medical Center, Boston, Massachusetts, United States

Lesley Ann Inker, MD, MS

Group or Team Name

• CKD-EPI and CKiD.

Background

In the United States, GFR is estimated using serum creatinine and the 2021 CKD-EPI equation for individuals > 18 years or the 2021 CKiD-U25 equation for those 1-25 years with CKD. These equations may result in different eGFR values at 18 years and older, leading to uncertainty in level of GFR.

Methods

We compared the CKD-EPI, CKiD-U25, and European Kidney Function Consortium (EKFC) equations in young adults (aged 18 to 40 years) in an independent dataset from which all three equations were developed (1491 participants from 21 studies). Performance compared to measured GFR was assessed as bias (median difference between mGFR and eGFR) and percentage of eGFR within 30% of mGFR (P₃₀).

Results

Mean (SD) age was 31.7 (6.0) years and mGFR was 92.7 (32.7) mL/min/1.73m². The equations provided similar estimates for participants with eGFR less than 60 mL/min/1.73 m². At eGFR ≥ 60, CKD-EPI yielded higher eGFR (Figure). For the CKD-EPI equation, there was minimal bias between mGFR and eGFR overall ([-0.5 (95%CI -1.5 to 0.7) mL/min/1.73m²], with small variation by GFR. In contrast, the CKiD-U25 equation moderately underestimated mGFR overall [7.2 (6.1, 8.3) mL/min/1.73m²], with larger bias at higher levels of eGFR. There was greater variation by age groups with CKiD-U25 than CKD-EPI, with larger bias at younger adult ages for CKiD (e.g. age 18-25 year, 12.0 (7.7, 15.5) for CKiD vs -3.3 (-5.0, 0.0) for CKD-EPI) vs older age (e.g. age 35-40, 4.8 (2.8, 6.7) for CKiD vs 1.0 (-0.3, 2.2) for CKD-EPI. Results for EKFC were similar to that of CKiD, with underestimation at higher levels of GFR and in the younger age group.

Conclusion

The results support use of the 2021 CKD-EPI equation for reporting of eGFR by clinical laboratories in individuals older than 18 years of age. For young adults with childhood CKD, our results support continuing use of the CKiD-U25 equation, during the transition to adult services, to maintain consistency of eGFR. Additional research in young adults to resolve differences observed at high levels of GFR and refine recommendations for use of eGFR equations is needed.

Funding

• NIDDK Support