Kidney Week

Abstract: TH-PO786

Risks Associated With Low eGFRcr, eGFRcys, and eGFRcr-cys at Older Age

Session Information

• Voices, Choices, and Outcomes of Older Adults with CKD
  November 03, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
  Abstract Time: 10:00 AM - 12:00 PM

Category: Geriatric Nephrology

• 1200 Geriatric Nephrology

Authors

• Fu, Edouard, Brigham and Women's Hospital, Boston, Massachusetts, United States

Edouard Fu,

• Carrero, Juan Jesus, Karolinska Institutet, Stockholm, Stockholm, Sweden

Juan Jesus Carrero,

• Sang, Yingying, Johns Hopkins University, Baltimore, Maryland, United States

Yingying Sang,

• Evans, Marie, Karolinska Institutet, Stockholm, Stockholm, Sweden

Marie Evans,

• Ballew, Shoshana, Johns Hopkins University, Baltimore, Maryland, United States

Shoshana Ballew,

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

Lesley Ann Inker,

• Grams, Morgan, Johns Hopkins University, Baltimore, Maryland, United States

Morgan Grams,

• Levey, Andrew S., Tufts Medical Center, Boston, Massachusetts, United States

Andrew S. Levey,

• Coresh, Josef, Johns Hopkins University, Baltimore, Maryland, United States

Josef Coresh,

Background

Understanding the risk consequences of CKD at older age has often been limited to kidney failure replacement therapy (KFRT) and all-cause mortality (ACM), and to GFR estimated using serum creatinine (eGFRcr). However, eGFRcr may be falsely elevated in the elderly due to low muscle mass. We sought to compare the risks of several clinically relevant outcomes associated with both eGFR_cr and cystatin C-based eGFR (unrelated to muscle mass), in elderly patients in routine health care.

Methods

We included all 79,995 patients (mean age 77 years, 50% female) in Stockholm region, Sweden (SCREAM) age 65+ years who undertook routine outpatient tests of IDMS calibrated creatinine and cystatin C on the same day during 2011-2018. We modeled CKD-EPI eGFR using creatinine (eGFRcr), cystatin C (eGFRcys) or both (eGFRcr-cys) as a spline in adjusted negative binomial and Cox regressions of subsequent risk for 7 clinical outcomes: acute kidney injury, KFRT, any hospitalization, heart failure hospitalization, major adverse cardiovascular events, cardiovascular and all-cause mortality.

Results

22% of older adults with creatinine testing also had routine cystatin C measurements. Figure 1 shows the HRs for each outcome at eGFR 30 or 60 vs. 80 ml/min/1.73m² by age group. Overall, eGFRcr was not as consistently associated across the range of outcomes as eGFRcys or eGFRcr-cys, especially at greater age. A U-shaped relationship was observed for all-cause mortality, cardiovascular mortality and hospitalization for eGFRcr, but not for eGFRcys or eGFRcr-cys (Figure 2).

Conclusion

eGFRcys and eGFRcr-cys reveal risk associations which are missed by eGFRcr. The U-shaped relationship with eGFRcr, not seen for eGFRcys, suggests the increased risk at high eGFRcr is associated with low creatinine generation, not true high GFR. Looking at outcomes beyond KFRT and mortality and using cystatin C allows for a better understanding of risks in CKD.