Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement

The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.


Risk of Septic Arthritis in Patients with Rheumatoid Arthritis Treated with Anti-TNF Therapy: Results From the BSR Biologics Register (BSRBR)

Galloway1,  J. B., Hyrich1,  K. L., Mercer1,  L. K., Dixon1,  W. G., Ustianowski2,  A. P., Watson1,  K. D., Lunt1,  M.

arc Epidemiology Unit, University of Manchester, Manchester, United Kingdom,
North Manchester General Hospital, Manchester, United Kingdom

Purpose:

Rheumatoid arthritis (RA) is associated with an increased risk of septic arthritis (SA). Clinical trials of anti-TNF therapy have not suggested an increased risk of SA, but there have been case reports suggesting a potential association.

Method:

Consecutive RA patients treated with anti-TNF therapy recruited between 10/01 and 5/08 by the BSRBR were followed 6 monthly via consultant and patient questionnaires until 12/31/08, end of follow up or death. A comparison cohort with active RA on disease modifying anti-rheumatic drugs (DMARD) was recruited and followed up in the same way. Incident cases of SA were identified from follow-up questionnaires and verified via medical records. SA was attributed to anti-TNF if it was diagnosed while on anti-TNF or within 90 days of the last dose. SA event rates in the anti-TNF and DMARD cohorts were compared using Cox proportional hazard ratio estimates adjusted for age, gender, disease severity, prior joint replacement, co-morbidity and steroid use. Missing baseline data were replaced using multiple imputations.

Results:

246 cases of SA were reported during the follow up period: 229/11757 in the anti-TNF cohort and 17/3515 in the comparison cohort. 179 cases could be attributed to anti-TNF using the "on drug plus 90 day" model. Incident rates were 5.0/1000 pyrs (95% CI 4.3, 5.8) in the anti-TNF cohort and 1.9/1000 pyrs (1.1, 3.0) in the controls. At least 51% of the SA in patients on anti-TNF occurred in native joints (Table). Patients on anti-TNF therapy were twice as likely to develop SA as controls (adjusted HR 2.0, 95% CI 1.1, 3.5). The individual anti-TNF drug adjusted results were etanercept HR 2.3, (CI 1.2, 4.4), infliximab HR 1.6, (CI 0.8, 3.2), and adalimumab HR 1.8, (CI 1.0, 3.5). Staphylococci were the most common organisms in both cohorts (DMARD 50%; anti-TNF 75%). 5 cases of intracellular infection (2 Listeria, 3 Salmonella) and 11 cases of Streptococcal SA (including 4 Streptococcus pyogenes) were reported (all in the anti-TNF cohort).

Table

 DMARD n=3513Anti-TNF On drug + 90 days n=11757
Pyrs follow up909435932
Total joint infections17179
Native joint infections, n(%)11 (65)91 (51)
Prosthetic joint infections, n(%)6 (35)54 (30)
Not stated, n(%)034 (19)
Unadjusted HR SA infections (95% CI)Ref2.7 (1.6 – 4.4)
Fully adjusted HR (95% CI)Ref2.0 (1.1 – 3.6)
Limited to native joints, fully adjusted HR (95% CI)Ref2.5 (1.2 – 5.0)
Limited to culture positive cases, fully adjusted HR (95% CI)Ref2.0 (1.1 – 3.6)

Conclusion:

Exposure to TNF inhibitor therapy is associated with an increased risk of SA in patients with RA. Careful vigilance for joint infections remains important with awareness of the potential range of pathogens. Antibiotic guidelines should incorporate this information.

To cite this abstract, please use the following information:
Galloway, J. B., Hyrich, K. L., Mercer, L. K., Dixon, W. G., Ustianowski, A. P., Watson, K. D., et al; Risk of Septic Arthritis in Patients with Rheumatoid Arthritis Treated with Anti-TNF Therapy: Results From the BSR Biologics Register (BSRBR) [abstract]. Arthritis Rheum 2009;60 Suppl 10 :2060
DOI: 10.1002/art.27132

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