Serum B cell activating factor (BAFF) as a biomarker for induction of remission with rituximab in ANCA-associated vasculitis

We examined whether serum B cell activating factor (BAFF) is useful for predicting the remission of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) following rituximab treatment. We used the Birmingham Vasculitis Activity Score (BVAS) 2008 version 3 for the evaluation of 27 patients with AAV 6 months after rituximab treatment. Those with BVAS = 0 achieved remission, whereas those with BVAS score > 0 did not achieve remission. We considered changes in serum BAFF before rituximab treatment, 1 month after treatment, and 6 months after treatment. In the remission group, the serum BAFF increased consistently. In the non-achieved group, serum BAFF was within the normal range. In addition, there was no statistically significant difference between the two groups in terms of serum BAFF before and 1 month after rituximab treatment. However, the serum BAFF level at 6 months after rituximab treatment was significantly higher in the remission group than in the non-achieved group. If serum BAFF does not increase after 6 months of rituximab in AAV, it may be assumed that there are residual B cells and plasma cells in the tissues. Enhanced treatment targeting B cells, including re-administration of rituximab or the addition of other immunosuppressive drugs, should be considered.