Incomplete concordance between laboratory and pathologic findings on post-induction kidney biopsy in pediatric patients with proliferative lupus nephritis.

Background: Proliferative lupus nephritis (LN) is associated with increased risk of progression to kidney failure. After initial kidney biopsy, the utility and timing of subsequent biopsies is unknown. There is known discordance between the laboratory parameters used to diagnose LN and the histopathologic classification. We explore the utility of a subsequent kidney biopsy in guiding treatment of LN to determine the factors that warrant follow-up kidney biopsy.

Methods: We conducted a single center retrospective cohort study of 30 SLE patients who underwent serial kidney biopsy for LN. Subjects were stratified based on their Childhood Arthritis and Rheumatology Research Alliance (CARRA) renal response into complete renal response (CRR) and incomplete renal response (IRR) groups at the time of second biopsy.

Results: Among 30 patients with LN, 11/18 in CRR group and 11/12 in IRR group had persistent proliferative nephritis at 1 ± 0.3 years after initial biopsy. Only SLEDAI score was associated with an increased risk of persistent proliferative nephritis (p = 0.03). Initial CARRA response category was associated with outcome at last follow-up (mean 4.5 years), with 11/18 CRR and 3/12 IRR achieving CRR at last follow-up at mean 4.5 years (p < 0.001). Kidney biopsy directly impacted clinical decision in 7/18 CRR patients in the CRR group who had therapy escalated or reduction withheld due to biopsy findings.

Conclusions: Available laboratory markers in LN are insufficient to identify children with ongoing proliferative nephritis. Follow-up kidney biopsy may be warranted for children with CRR at 1 year after initial biopsy.