CureGN-Diabetes Study: Rationale, Design, and Methods of a Prospective Observational Study of Glomerular Disease Patients with Diabetes

Abstract

Glomerular diseases (GDs) represent the third leading cause of end-stage kidney disease (ESKD) in the US Diabetes was excluded from the CureGN Study, an NIH/NIDDK-sponsored observational cohort study of four leading primary GDs: IgA nephropathy (IgAN), membranous nephropathy (MN), focal segmental glomerulosclerosis (FSGS), and minimal change disease (MCD). CureGN-Diabetes, an ancillary study to CureGN, seeks to understand how diabetes influences the diagnosis, treatment, and outcomes of GD. It is a multicenter, prospective cohort study, targeting an enrollment of 300 adults with prevalent type 1 or type 2 diabetes and MCD, FSGS, MN, or IgAN, with first kidney biopsy obtained within 5 years of enrollment in 80% (20% allowed if biopsy after 2010). CureGN and Transformative Research in DiabEtic NephropaThy (TRIDENT) provide comparator cohorts. Retrospective and prospective clinical data and patient-reported outcomes are obtained. Blood and urine specimens are collected at study visits annually. Kidney biopsy reports and digital images are obtained, and standardized pathologic evaluations performed. Light microscopy images are uploaded to the NIH pathology repository. Outcomes include relapse and remission rates, changes in proteinuria and estimated glomerular filtration rate, infections, cardiovascular events, malignancy, ESKD, and death. Multiple analytical approaches will be used leveraging the baseline and longitudinal data to compare disease presentation and progression across subgroups of interest. With 300 patients and an average of 3 years of follow-up, the study has 80% power to detect a HR of 1.4-1.8 for time to complete remission of proteinuria, a rate ratio for hospitalizations of 1.18-1.56 and difference in eGFR slope of 6.0-8.6 mL/min/year between two groups of 300 participants each. CureGN-Diabetes will enhance our understanding of diabetes as a modifying factor of the pathology and outcomes of GDs and support studies to identify disease mechanisms and improve patient outcomes in this understudied patient population.

Keywords: Cure Glomerulonephropathy Network; Diabetes; Focal segmental glomerulosclerosis; Glomerular disease; IgA nephropathy; IgA vasculitis; Membranous nephropathy; Minimal change disease.

Fig. 1.

Schematic representation of the study cohorts with glomerular disease and/or diabetes that feed into and/or provide comparator populations to the CureGN-Diabetes cohort. DGS, diabetic glomerulosclerosis; FSGS, focal and segmental glomerulosclerosis; GN, glomerulonephritis; IgA, IgA nephropathy and IgA vasculitis; MN, membranous nephropathy.

Fig. 2.

Aims for the CureGN-Diabetes study.

Fig. 3.

Timeline for study visits in CureGN-Diabetes. FSGS, focal and segmental glomerulosclerosis; GN, glomerulonephritis; IgA, IgA nephropathy and IgA vasculitis; MN, membranous nephropathy; PRO, patient-reported outcomes.