Background: We hypothesized that the levels of red cell distribution width (RDW) would correlate with lupus nephritis (LN) disease activity, therapeutic response after induction therapy, and its rise would be associated with future renal relapse in patients who had achieved clinical remission.
Methods: The associations of RDW and Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), renal response, and renal relapse after induction therapy were examined in 172 biopsy-proven LN patients at the Division of Nephrology, Huashan Hospital Fudan University between 2007 and 2017.
Results: The median RDW of LN patients was significantly higher than that of healthy individuals (p < 0.001). Baseline RDW demonstrated positive correlation with baseline SLEDAI (r = 0.239, p = 0.004). Overall RDW after induction treatment was significantly decreased (p = 0.005), especially in the complete remission (CR) group (p = 0.02), and the partial remission (PR) group had a decreasing trend (p = 0.09), while the change of RDW in the no response (NR) group was not statistically significant (p = 0.70). Among the 153 patients who achieved remission after induction therapies, 37 (24.2%) patients developed 42 episodes of subsequent renal flare during a median follow-up of 36.0 (IQR, 20 - 66) months. The median time from remission to renal flare was 18.0 (IQR, 7.0 - 45.0) months. The overall renal flare rate was 0.065 relapse per patient-year. During follow up, 54 RDW rises (defined as more than 0.5% increase in RDW) were identified. There were 33 episodes (61.1%) of renal flares in patients with RDW rises, while there were only 9 renal flares (8.65%) in 104 patients without RDW rise (p < 0.001). Survival analysis showed that RDW rise was associated with a significantly higher risk of future renal relapse (adjusted HR, 14.03; 95% CI, 5.29 to 37.20; p < 0.001).
Conclusions: In addition to correlating with disease activity and therapeutic response to induction therapy in patients with LN, RDW rise is a significant predictor of future renal relapse in patients who achieve remission.