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Abstract: SA-PO399

Predictors of Non-Linearity in eGFR Trajectories in the Nephrotic Syndrome Study Network (NEPTUNE)

Session Information

Category: Glomerular Diseases

  • 1203 Glomerular Diseases: Clinical, Outcomes, and Trials

Authors

  • Smith, Abigail R., Arbor Research Collaborative for Health, Ann Arbor, Michigan, United States
  • Ji, Nan, Arbor Research Collaborative for Health, Ann Arbor, Michigan, United States
  • Zee, Jarcy, Arbor Research Collaborative for Health, Ann Arbor, Michigan, United States
  • Nair, Viji, University of Michigan, Ann Arbor, Michigan, United States
  • Mariani, Laura H., Arbor Research Collaborative for Health, Ann Arbor, Michigan, United States
Background

Surrogate outcomes for end-stage kidney disease (e.g. eGFR slope or 40% decline) often assume linear changes, which may not always reflect true eGFR trajectories. The objective of this study was to identify patient characteristics associated with non-linear eGFR trajectories in a cohort of patients with nephrotic syndrome.

Methods

Data were obtained from the NEPTUNE study, a multicenter observational cohort study of adult and pediatric patients with >500mg/day of proteinuria enrolled at the time of clinically indicated biopsy or initial presentation of disease without biopsy (pediatric patients). eGFR was calculated using the CKD-Epi formula for patients ≥18 years old and modified CKiD-Schwartz formula for patients <18. Probability of non-linearity (PNL) was calculated using Bayesian smoothing of individual eGFR trajectories, and patient demographic and clinical variables and follow-up time were used to predict PNL in multivariable linear regression.

Results

385 patients with ≥3 eGFR measurements and ≥1 year of follow-up were included (median follow up time 39 months). Median PNL was 0.047, with 15.6% and 6.5% having a PNL >50% and >75%, respectively. Higher baseline eGFR and UPCR, black race and steroid use at baseline were associated with higher PNL (9% increase per 10 unit increase in eGFR, p=0.001; 4% increase per unit increase in UPCR, p=0.011; 40% higher in black patients, p=0.038; 56% higher with steroid use at baseline, p=0.008, Table). Age and maximum follow-up time were associated with lower PNL (16% decrease per 10 year increase in age, p<0.001; 34% decrease per year increase in follow-up time, p<0.001).

Conclusion

While non-linear eGFR trajectories were common in this cohort, increasing follow-up time resulted in more linear trajectories. Higher baseline eGFR, younger age, black race, and steroid use were associated with higher probability of non-linear eGFR trajectories. Surrogate outcomes that assume linearity may be valid with sufficient follow-up.