Childhood-onset lupus nephritis in the Childhood Arthritis and Rheumatology Research Alliance Registry: Short-term kidney status and variation in care

Objective: Characterize short-term kidney status and describe variation in early care utilization in a multi-center cohort of patients with childhood-onset systemic lupus erythematosus (cSLE) and nephritis. Methods: We analyzed previously collected prospective data from North American cSLE patients with kidney biopsy-proven nephritis enrolled in the Childhood Arthritis and Rheumatology Research Alliance (CARRA) Registry from March 2017 through December 2019. We determined the proportion of patients with abnormal kidney status at the most recent registry visit and applied generalized linear mixed model to identify associated factors. We also calculated frequency of medication use, both during induction and ever recorded. Results: We identified 222 patients with kidney biopsy-proven nephritis, with 64% class III/IV nephritis on initial biopsy. At the most recent registry visit at median (IQR) of 17 (8-29) months from initial kidney biopsy, 58/106 (55%) with available data had abnormal kidney status. This was associated with male sex (OR 3.88, 95%CI 1.21-12.46) and age at cSLE diagnosis (OR 1.23, 95%CI 1.01-1.49). Patients with class IV nephritis were more likely than class III to receive cyclophosphamide and rituximab during induction. There was substantial variation in mycophenolate, cyclophosphamide, and rituximab ever use patterns across rheumatology centers. Conclusion: In this cohort with predominately class III/IV nephritis, male sex and older age at cSLE diagnosis were associated with abnormal short-term kidney status. We also observed substantial variation in contemporary medication use for pediatric lupus nephritis between pediatric rheumatology centers. Additional studies are needed to better understand the impact of this variation on long-term kidney outcomes.