NEW YORK (Reuters Health) – The rate of serious bacterial infections in patients with rheumatoid arthritis (RA) is not higher among those taking tumor necrosis factor (TNF)-alpha blockers compared to those taking methotrexate, a new study suggests.

"Even though opportunistic infections have been linked to anti-TNF alpha therapy, the association with serious bacterial infections, a far more common cause of morbidity in this population, has not been thoroughly assessed," Dr. Sebastian Schneeweiss of Harvard Medical School, Boston and colleagues note in the June issue of Arthritis & Rheumatism.

In a cohort of 15,597 RA patients who initiated a disease-modifying anti-rheumatic drug (DMARD) between 1995 and 2003, the researchers found no increase in the rate of bacterial infections among initiators of anti-TNF alpha therapy compared with initiators of methotrexate therapy. "This finding was independent of concomitant DMARD use and persisted after adjusting for other predictors of infections," they report.

Overall, the incidence of serious bacterial infections averaged 2.2 per 100 patient-years in this population.

Consistent with other studies, note the researchers, glucocorticoid therapy doubled the rate of serious bacterial infections as compared with methotrexate, independent of previous DMARD use, with a clear dose-response relationship for doses greater than 5 milligrams per day.

"This threshold for safe low-dose glucocorticoids use with regard to outcomes of infection corroborates the findings of a meta-analysis of randomized trial," Dr. Schneeweiss and colleagues point out.

Summing up, the researchers say their findings are consistent with at least two hypotheses: "first, that in routine care, physicians seem to be able to manage RA well with anti-TNF alpha therapy with regard to the risk of serious infections; and second, that improvements in patient functioning, with anti-TNF alpha and methotrexate therapy may counteract some of the immunosuppressive effects of these drugs."