Kidney Week

Abstract: SA-PO807

Proteinuria as a Surrogate Predictor of Kidney Failure in Both C3 Glomerulopathy and Primary Immune-Complex Membranoproliferative Glomerulonephritis

Session Information

• C3G, TMA, MGRS, Amyloidosis, and More
  October 26, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

• 1402 Glomerular Diseases: Clinical, Outcomes, and Therapeutics

Authors

• Caravaca-Fontan, Fernando, Instituto de Investigacion Hospital 12 de Octubre, Madrid, Comunidad de Madrid, Spain

Fernando Caravaca-Fontan, MD, PhD

• Praga, Manuel, Universidad Complutense de Madrid, Madrid, Madrid, Spain

Manuel Praga, MD

Group or Team Name

• GLOSEN Group.

Background

C3 glomerulopathy (C3G) and primary immune complex membranoproliferative glomerulonephritis (IC-MPGN) are rare glomerular diseases sharing similar etiology and pathogenesis. While some studies have shown association between changes in proteinuria and kidney outcomes in C3G, the prognostic significance of proteinuria changes in IC-MPGN remains largely unexplored.

Methods

Multicenter, retrospective cohort study in 37 nephrology departments belonging to GLOSEN group. All patients fulfilling diagnostic criteria of C3G were included, and secondary causes of IC-MPGN were carefully ruled out. A joint modelling of linear mixed-effects models was applied to assess the underlying trajectory of a repeatedly measured proteinuria at 0,1,3,6,12,24,60 or last follow-up, and a Cox model to evaluate the association with the risk of kidney failure.

Results

The study group consisted of 154 patients: 124 with C3G (81%) and 30 IC-MPGN (19%), with a mean age of 33±17 years. Median baseline eGFR was 55 ml/min/1.73m² (IQR 24–106) and proteinuria 3 g/day (IQR 1.7–6). No significant clinical or histologic baseline differences were observed across groups. During a median follow-up of 65 months (IQR 30–123), 55 patients (36%) reached kidney failure, without differences between groups. The longitudinal change in proteinuria exhibited a robust association with this outcome, where each 1g/day increase was linked to a 3.4-fold rise in the risk. A ≥30% proteinuria reduction over time was associated with a lower risk of kidney failure (HR 0.97; 95% CI 0.94–0.99; p<0.001), as was a ≥50% proteinuria reduction over time (HR 0.92; 95% CI 0.85–0.95; p<0.001). Results were consistent in both C3G and IC-MPGN. A ≥30% proteinuria at 6 months or a ≥50% proteinuria reduction at 12 months were associated with a slower eGFR decline over time. These results were also confirmed in patients aged >12 years at baseline, eGFR ≥30 ml/min/1.73m² and proteinuria ≥1g/day at baseline.

Conclusion

Proteinuria reduction is associated with improved kidney outcomes in both C3G and primary IC-MPGN.