The risk of joint infections in people with rheumatoid arthritis receiving anti-TNF therapies
By Dr Kimme Hyrich and Dr James Galloway
Taken from NRAS magazine, Winter 2011
Anti-TNF therapies, which include etanercept, infliximab, adalimumab, certolizumab and golimumab, have helped improve symptoms for many people with rheumatoid arthritis (RA). However, because the drugs act on the immune system they may also make people more likely to develop infections. A recent study using data from patients enrolled in the British Society for Rheumatology Biologics Register (BSRBR) looked to see if anti-TNF therapy increased the risk of infections in the joints (septic arthritis). This is a potentially serious condition which usually requires hospitalization, antibiotics and possible surgery.
The BSRBR started in 2001 with the aim of studying the long-term safety of anti-TNF therapy in people with RA. The BSRBR is an observational study and observes what happens to people receiving different treatments for their arthritis. Since then, almost 20,000 individuals from across the UK have agreed to take part in this study. Information is provided to the study team in Manchester on a regular basis from their rheumatology doctors and nurses. The study collects information on patients receiving anti-TNF therapy for their arthritis as well as from people receiving standard therapies such as methotrexate or sulphasalazine. The development of side effects is compared between these 2 groups to see if they are more common with one treatment over another.
Overall, joint infections were very rare, with only 199 cases reported. Of these, 179 were in patients receiving anti-TNF therapy and 20 were receiving standard therapy.
As more patients in the study were receiving anti-TNF therapy, the researchers determined that the rate of infection was 4 per 1000 treated anti-TNF patients and 2 per 1000 standard therapy treated patients. Therefore, overall the risk was doubled in the anti-TNF group.
What does this mean for patients receiving or considering anti-TNF therapy?
Although the relative risk was 2-fold higher in patients receiving anti-TNF therapies compared to those who were not, it is important to remember that overall the risk of joint infection was very low and most people who take anti-TNF therapy will not develop an infection in their joint. Another way to explain the risk would be to say that a rheumatologist would have to treat 500 people with anti-TNF therapy for him/her to see one additional person develop a joint infection.
This information will help doctors and patients weigh up the potential risks and benefits of anti-TNF treatment. The research also provides information to doctors about this rare but serious diagnosis and to consider it in people who have new or worsening joint pain and swelling or other signs of infection.
Galloway JB, Hyrich KL, Mercer LK, Dixon WG, Ustianowski AP, Helbert M, Watson KD, Lunt M, Symmons DP; BSR Biologics Register.
Risk of septic arthritis in patients with rheumatoid arthritis and the effect of anti-TNF therapy: results from the British Society for Rheumatology Biologics Register. Ann Rheum Dis. 2011 Oct;70(10):1810-4.