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Abstract: SA-PO922

Using the Difference in Estimated Glomerular Filtration Rate by Cystatin C vs. Creatinine to Improve the Ability to Predict the Competing Risk of Death or ESKD

Session Information

Category: CKD (Non-Dialysis)

  • 2202 CKD (Non-Dialysis): Clinical‚ Outcomes‚ and Trials

Authors

  • Potok, O. Alison, University of California San Diego, La Jolla, California, United States
  • Hallan, Stein I., Norges teknisk-naturvitenskapelige universitet, Trondheim, Trøndelag, Norway
  • Ix, Joachim H., University of California San Diego, La Jolla, California, United States
  • Katz, Ronit, University of Washington, Seattle, Washington, United States
  • Bansal, Nisha, University of Washington, Seattle, Washington, United States
  • Rifkin, Dena E., University of California San Diego, La Jolla, California, United States
Background

Glomerular filtration rate (GFR) can be estimated using serum creatinine or cystatin C. Prior research shows that a greater negative difference in estimated GFR by cystatin C vs. creatinine (eGFRDiff = eGFRcys - eGFRcr) associates with frailty, hospitalizations, and mortality. We aimed to determine whether including eGFRDiff into existing predicting tools for kidney failure (KFRE) and mortality risk (MREK) would increase their accuracy in older persons with chronic kidney disease (CKD). We hypothesized that the MREK with eGFRDiff would perform better than the current equation, while the KFRE with eGFRDiff would perform as well as the current equation.

Methods

1146 community-living participants of the Norwegian HUNT study (age >65, eGFRcr < 45 mL/min/1.73m2) were evaluated. eGFRDiff was calculated as eGFRcys – eGFRcr using the CKD-EPI 2012 and 2009 equations respectively.
Standard KFRE and MREK scores were computed for each participant. Outcomes were end stage kidney disease (ESKD) and death at 5 years. C-statistics were computed for each predictor (KFRE and MREK) with and without the addition of eGFRDiff.

Results

Mean ±SD age was 80±7 years, eGFRcr was 36±8, eGFRcys was 37±15, and eGFRDiff was 1.04±12 mL/min/1.73m.2 Over the 5 year observation period, 60 participants (5%) reached ESKD and 444 died (39%), corresponding to KFRE and MREK predictions of 5 (10) % and 30 (19) %, respectively. Diagnostic accuracy measured as C-statistics [95% confidence interval] were 92.7% [88.9; 96.5] for KFRE alone, 93.5% [90.4; 96.6] for KFRE and eGFRDiff (Figure 1a, p=0.31), 70.6% [67.2; 74.0] for MREK alone, 73.4% [70.1; 76.5] for MREK and eGFRDiff (Figure 1b, p<0.01)

Conclusion

The eGFRdiff improves the accuracy of the mortality risk but not the kidney failure risk equation in older patients with advanced CKD. Thus, incorporation of eGFRDiff may improve estimation of the competing risk of death vs. ESKD in older adults.

Funding

  • NIDDK Support