Certain arthritis drugs affect TB risk

PARIS, July 1 (UPI) -- The risk of tuberculosis for patients who take arthritis drugs differs from that of the French population at large depending on the agent used, researchers say.

Treatment with anti-tumor necrosis factor agents is recognized as a risk factor for TB in patients with immune-mediated inflammatory diseases such as rheumatoid arthritis, ankylosing spondylitis, Crohn's disease, psoriatic arthritis and psoriasis.

Xavier Mariette of the Universite Paris-Sud says most TB cases develop as a result of reactivation of a latent TB infection, and health authorities worldwide recommend screening for latent TB and treating patients before initiating anti-TNF treatment.

The researchers set up a national registry in France to collect all cases of TB occurring during a three-year period in patients receiving anti-TNF therapy for any reason. Researchers collected data on 69 cases of TB, assessing risk factors for TB before anti-TNF therapy began and anti-TNF treatment history.

The study, published in Arthritis & Rheumatism, determined the risk of TB is higher for patients receiving anti-TNF monoclonal antibody therapy -- infliximab or adalimumab -- than for those receiving soluble TNF receptor therapy -- etanercept.

The mechanism by which TNF antagonists reactivate latent TB is not fully understood, but the authors suggest that differences in the action of the two types of anti-TNF agents in specific T helper cells -- which play an important role in maximizing the capabilities of the immune system -- and T regulatory cells -- which suppress activation of the immune system -- may help explain the differences in the risk of TB observed.