A brief report published early online in Arthritis and Rheumatism describes factors predicting non-response to rituximab in patients with rheumatoid arthritis (RA), and the response to re-treatment in these patients.

The authors describe outcomes from a series of 158 patients. Highly sensitive flow cytometry (HSFC) was used to determine persistent circulating B cells at week 2, as there is evidence that this is associated with lack of response. Complete data were available for 103 patients: 65 who responded to the first cycle of rituximab treatment and 38 who did not. Of the non-responders, 25 received a second treatment cycle at least 6 months after the first.

In the analyses, complete B-cell depletion measured by HSFC predicted a response to treatment: 38% of responders had complete depletion compared to 12% of non-responders. Those who had complete B-cell depletion after re-treatment also responded. The authors suggest that their data support the strategy of re-treating patients with RA who do not respond to a first course of rituximab, and that HSFC is a useful tool to assess therapeutic strategies.