Listing J et al. (2005) Infections in patients with rheumatoid arthritis treated with biologic agents. Arthritis Rheum 52: 3403–3412

Rheumatoid arthritis (RA) patients treated with biologic agents have a higher risk of infection than patients treated with conventional disease-modifying antirheumatic drugs (DMARDs), the German prospective cohort study RABBIT (RA–Observation of Biologic Therapy) has found.

A German national register was established in 2001 to investigate biologic therapy, following observations of serious adverse events from tumor necrosis factor (TNF) inhibitors. In the recent paper by Listing and colleagues, this registry was used to estimate the incidence of serious and nonserious infections 1 year after initiation of biologic therapy.

As patients with RA already have an increased risk of infection compared with the general population, RA patients receiving biologic therapy were compared with RA patients receiving DMARDs. There were 1,529 patients analyzed in the trial, including 512 treated with etanercept, 346 treated with infliximab, 70 treated with anakinra, and 601 treated with conventional DMARDs. Assessments were carried out at baseline and at 3, 6 and 12 months.

Infections were observed in 204 patients. The relative risk of serious adverse events was 2.7–2.8 in the biologic group compared with the DMARD group, and for adverse events in general the relative risk was 3.3–4.1. Although the groups had different predispositions, the investigators estimated that biologic therapy caused two-thirds of the increased incidence of adverse events. This estimate should be further validated by trials that include more patients and more risk factors in the analysis.