ASN's Mission

To create a world without kidney diseases, the ASN Alliance for Kidney Health elevates care by educating and informing, driving breakthroughs and innovation, and advocating for policies that create transformative changes in kidney medicine throughout the world.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005


The Latest on Twitter

Kidney Week

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


  • 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

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.


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.


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).


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.