Fig. 2.

Association between rituximab serum levels and time to relapse and to B cell redetection

Serum rituximab levels by ELISA at each visit were analysed as tertiles, the lowest tertile (tertile 1) considered as the reference for time to event comparison with tertiles 2 and 3 (respectively, medium and highest rituximab levels) using Cox proportional hazards models. Time to any flare and time to severe flare were analysed in patients who reached complete remission, and time to B cell redetection (defined as B cells ≥10/µl) was analysed considering flare as a competing event (since treatments administered for flares could influence the duration of B cell depletion).