Background In patients with Lupus Nephritis (LN), clinical response to treatment and renal histopathology have been shown to be discordant. We investigated whether per-protocol repeat renal biopsies are predictive of LN relapses and long-term impairment of renal function.
Methods Forty-two patients with an incident biopsy-proven active proliferative (class III/IV ± V) LN from the LN database of the Université catholique de Louvain were included in the present retrospective study. Per-protocol repeat kidney biopsies were performed in all patients after a median time of 24.3 (IQR: 21.3–26.2) months. The NIH activity index (AI) and chronicity index (CI) scores were assessed in both baseline and repeat biopsies.
Results Despite a moderate correlation between urinary protein/creatinine (U-P/C) ratios and AI scores at repeat biopsy (r=0.48; P=0.001), ten patients (23.8%) with U-P/C ratios <1.0 g/g still had a high degree of histological activity (AI score >3; figure 1). High AI scores in repeat biopsies were associated with an increased probability and/or shorter time to renal relapse (N=11) following the repeat biopsy (HR: 1.2; 95% CI: 1.1–1.3; P=0.007), independently of proteinuria levels. High NIH CI scores in repeat biopsies were associated with a sustained increase in serum creatinine levels corresponding to ≥120% of the baseline value (HR: 1.8; 95% CI: 1.1–2.9; P=0.016) through a median follow-up time of 131.5 (IQR: 73.8–178.2) months. Baseline AI/CI scores were not predictive of these outcomes.
Conclusions Our results highlight the usefulness of per-protocol repeat biopsies as an integral part of the treatment evaluation, also in patients who have shown adequate clinical response.
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