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Abstract: PO1681

Using the Difference in Estimated Glomerular Filtration Rate by Cystatin C vs. by Serum Creatinine (eGFRDiff) to Assess Muscle Mass and Frailty in Older Adults

Session Information

Category: Geriatric Nephrology

  • 1100 Geriatric Nephrology

Authors

  • Potok, O. Alison, University of California San Diego, La Jolla, California, United States
  • Ix, Joachim H., University of California San Diego, La Jolla, California, United States
  • Shlipak, Michael, San Francisco VA Medical Center, San Francisco, California, United States
  • Bansal, Nisha, University of Washington, Seattle, Washington, United States
  • Katz, Ronit, University of Washington, Seattle, Washington, United States
  • Kritchevsky, Stephen B., Wake Forest University School of Medicine, Winston-Salem, North Carolina, United States
  • Rifkin, Dena E., University of California San Diego, La Jolla, California, United States
Background

Preliminary work has shown that the difference in estimated glomerular filtration rate by cystatin C vs by creatinine (eGFRDiff) is associated with frailty and mortality. As creatinine is influenced by muscle mass, more so than cystatin, we aim to determine whether muscle mass explains the relationship between eGFRDiff and frailty.

Methods

In the Health Aging Body Composition study, 2980 (97% of HABC) had baseline serum creatinine, cystatin C, and muscle mass measures on imaging. eGFRs were calculated using CKD-EPI equations (cystatin-based [eGFRCys] and creatinine-based [eGFRCr] respectively), and eGFRDiff was eGFRCys – eGFRCr. Total thigh muscle area was evaluated on computed tomography. Frailty was scored on a continuous scale including standing and walking tasks; the lowest quartile of scores were defined as frail.

Results

Mean age was 74 (±3) years, eGFRCys was 72 (±19), eGFRCr was 68 (±15), and eGFRDiff was 4 (±14) mL/min/1.73m2. Compared to participants with minimal difference in eGFR (within 10 mL/min/1.73m2), those in the positive eGFRDiff group (>10 mL/min/1.73m2) were less likely to have fallen in the past year (19% vs. 21%), had stronger grip strength (31 vs. 30kg) and walked faster (1.22 vs. 1.17m/s). Higher eGFRDiff was significantly associated with larger thigh muscle area. In cross-sectional analyses, each 1 SD increment in eGFRDiff was associated with 30% lower odds of frailty in models adjusted for demographics, cardiovascular risk factors, and chronic kidney disease category (Table). This relationship was attenuated when adjusting for measures of muscle mass and strength but remained statistically significant.

Conclusion

The difference eGFRCys - eGFRCr provides information on older adults’ functional status which is only partially explained by muscle quantity and quality.

Cross-sectional association of eGFRDiff with frailty in HABC participants
Outcome: FraileGFRDiff (per SD =14 increase)
n=2980OR (95%CI)p value
unadjusted0.69 (0.63; 0.76)<0.0001
Model 1*0.70 (0.64; 0.78)<0.0001
Model 2**0.79 (0.71; 0.89)<0.0001

*adjusted for age gender race education BMI serum albumin CRP smoking HTN, antiHTN meds, diabetes CKD category by eGFRCr **further adjusted for total thigh muscle area & grip strength