To observe the course of the disease activity in rheumatoid arthritis (RA) patients treated with the standard infliximab dosing regimen and to adjust treatment guided by the pattern of disease activity.
All RA patients starting infliximab treatment were included and observed for at least 37 weeks. At infusion 4 (week 14), European League Against Rheumatism response was assessed. In moderate responders the dose was unchanged and the disease activity was carefully observed. In case of stable disease activity, the dose was increased at infusion 5 (week 22). In case of a temporary response the interval was reduced. Paired t-testing was applied to the disease activity score with 28-joint counts (DAS28) at week 22 and study endpoint.
A total of 76 patients were included. Response after 14 weeks: good 22 (29%) patients, moderate 26 (34%) patients, and non-response in 21 patients. Seven patients (9%) dropped out before week 14 due to adverse events (5) or patients' initiative (2). In patients with moderate response, the following disease course between infusion 4 and 5 was observed: improvement to good response 6, temporary response 6, stable disease activity 6, drop out 8. In moderate responders, interval reduction and dose increase resulted in a decrease in mean DAS28 from 5.1 to 3.6 [P = 0.005, mean interval 5.6 weeks, mean infliximab dose 4.8 mg/kg/8 week (endpoint)] and from 4.1 to 3.6 [P = 0.04, mean infliximab dose 7.3 mg/kg/8 week (endpoint)], respectively.
Three different patterns of disease activity were observed in moderate responders after 14 weeks of infliximab treatment, i.e. further improvement, no change in disease activity or a temporary response. Both interval reduction and dose increase significantly reduced disease activity, however, with different mean infliximab dosages. In good responders the response was often sustained over follow-up, whereas non-responders showed modest or no improvement despite dose adjustments.