Kidney Week

Abstract: TH-PO854

Sex-Free Estimation of eGFR Preferentially Reclassifies Women as Having Better Kidney Function

Session Information

• Race, Ethnicity, and Gender in Kidney Health and Care
  October 24, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Diversity and Equity in Kidney Health

• 900 Diversity and Equity in Kidney Health

Authors

• Steinbrenner, Inga, Institute of Genetic Epidemiology, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany

Inga Steinbrenner, MS, MSc

• Kottgen, Anna, Institute of Genetic Epidemiology, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany

Anna Kottgen, MD, MPH

• Schaeffner, Elke, Institute of Public Health, Charité – Universitätsmedizin Berlin, Berlin, Germany

Elke Schaeffner, MD, MS

• Eckardt, Kai-Uwe, Department of Nephrology and Hypertension, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen-Nürnberg, Germany

Kai-Uwe Eckardt, MD

• Schultheiss, Ulla T., Institute of Genetic Epidemiology, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany

Ulla T. Schultheiss, MD

Background

Chronic kidney disease (CKD) is staged based on estimated glomerular filtration rate (eGFR, G categories) and urinary-creatinine-to-albumin-ratio (UACR; A categories). Using the cystatin-C based CKD-EPI equation (CKD-EPI) to estimate GFR, women are more likely to be diagnosed with CKD, while men have higher incidence of kidney replacement therapy (KRT). This discrepancy could stem from an overestimation of CKD prevalence and severity on eGFR equations in women, or a slower CKD progression in women compared to men. Pottel et al. introduced a cystatin C-based eGFR equation (EKFC) no longer requiring sex information showing less bias compared to measured GFR than previous equations. We therefore assessed reclassification of CKD stages in >5,000 participants diagnosed with CKD in the German CKD (GCKD) study with the EKFC compared to the CKD-EPI equation in a sex-specific manner.

Methods

The GCKD study’s main inclusion criteria were an eGFR between 30-60 or >60 mL/min/1.73m² in the presence of a UACR >300 mg/g. Of 5,217 participants, 91.5% fulfilled the criteria of decreased eGFR, while 8.5% were enrolled based on UACR. Cystatin C was measured from baseline serum samples using a particle-enhanced turbidimetric immunoassay (Tina-quant, Roche). The CKD-EPI and EKFC equations were used to estimate GFR. Reclassification of proportions by sex using the KDIGO G stages was done by comparing the CKD-EPI equation with the EKFC equation.

Results

Among 5,161 participants (60% men), clear sex-specific differences were detected when applying the EKFC equation: compared to the CKD-EPI equation, women in G3a/b were 2-4.5 times more likely to be reclassified to a “milder” G category of CKD (Table).

Conclusion

The observed reclassification of women is consistent with the lower incidence of KRT in women and may help to resolve the apparent discrepancy of higher CKD prevalence yet lower KRT incidence observed with previous equations. Future studies should assess the relationship between EKFC estimates and CKD progression.

Excerpt: Reclassification of G categories by sex in GCKD study participants in G3a/b by the cystatin C-based EKFC eGFR equation without sex and cystatin C-based CKD-EPI eGFR equation including sex.