Clinical Outcomes in the Nephrotic Syndrome Study Network: Disease Burden and Treatment Patterns over Time.

Introduction: Among patients with proteinuric glomerular diseases, there is a paucity of high-quality evidence and substantial variation in practice patterns among nephrologists. Our objective was to describe the clinical presentation, treatment patterns, and outcomes of patients with biopsy-proven glomerular diseases in a contemporary, well-phenotyped, diverse cohort. Methods: The Nephrotic Syndrome Study Network (NEPTUNE) is a prospective observational cohort study of children and adults with proteinuric glomerular diseases enrolled at 23 centers in the USA and Canada since 2009. We included participants who underwent their first clinically indicated kidney biopsy demonstrating minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), or membranous nephropathy (MN). We described demographic and clinical characteristics at the time of biopsy and baseline visits. We analyzed treatment patterns for participants with and without immunosuppressive therapy (IST) use prior to biopsy. We described clinical outcomes including complete remission (CR) and proteinuria, stratified by IST use, at biopsy and up to 36 months' follow-up. Results: Among 507 NEPTUNE participants who underwent biopsy, 203 were classified as having FSGS, 193 as having MCD, and 111 as having MN. Corticosteroid exposure was high overall and highest among MCD patients. Substantial heterogeneity in treatment choices was evident, particularly among those initiating second-line therapy. The rate of kidney failure was highest, and CR rates were lowest, among patients with FSGS, who experienced ∼50% cumulative probability of first remission at 36 months after biopsy. At 36 months, 49.5% of all patients were not in CR; 19.3% were not in CR despite being on IST. Additionally, 20.2% of patients had proteinuria >1.5 g/g; among those on IST at their 36-month visit, 26.3% had UPCR >1.5 g/g. Conclusion: A substantial proportion of patients were not in remission and had persistent proteinuria despite being on IST 3 years after their first biopsy.