Biologic disease modifying anti-rheumatic drugs (bDMARDs) have significantly improved the prognosis for patients with rheumatoid arthritis (RA). However, due to their immunosuppressive nature, concerns remain about the potential for infection in patients receiving these medications.
To evaluate the incidence of serious infections (SI) in a Western Australian cohort of patients with RA who are receiving bDMARDs. The role of confounders including age, gender, comorbidities and use of glucocorticoids was also evaluated. The incidence of SI was defined as any infection necessitating admission to the hospital and the use of antibiotics.
A 10-year retrospective review was conducted of all patients with RA who were receiving bDMARDs at three tertiary hospitals in Western Australia. Discharge summaries and all available clinic letters were reviewed and patient demographics and clinical data were collected. Pearson Chi-squared test and Student's t-test were used for comparing demographic factors and clinical variables between the groups with SI and those without.
One hundred and two patients met the inclusion criteria for the period 2006-2016, 25 of whom had been admitted with SI, accounting for a total of 46 admissions. Skin and soft tissue infections were the most common (28%) followed by respiratory infections (26%) and urinary tract infections (20%). The incidence rate of SI was 8.98 per 100 person years. The rate was lowest with adalimumab (5.27 per 100 person years) and highest with infliximab (34.5 per 100 person years). Those with SI were older (68 years vs 60 years; P = 0.02) and had been on bDMARDs for longer period of time (6.05 years vs 4.68 years; P = 0.04). There was no significant increase in length of stay due to co-administration of glucocorticoids. The presence of comorbidities did not play a significant role in increasing the risk of SI.
Age and duration of bDMARD use were statistically significant factors associated with an increased risk of SI. Comorbidities did not play a significant role in increasing the incidence of SI. Patients who were on both glucocorticoids and bDMARDs did not have a significant increase in length of stay when compared with patients who were just on bDMARDs. More research is needed in this area with larger numbers to draw statistically significant conclusions regarding the role of comorbidities in SI risk and the individual infection risk associated with each bDMARD.