Background The increased risk of opportunistic infections (OIs) in rheumatoid arthritis (RA) patients who started biologic disease modifying anti-rheumatic drugs (DMARDs) has been well known. However, it has not been studied regarding the increased risk of OIs in the early stage of RA.

Objectives To study the increased risk of incidence rate (IR) of OIs in early RA patients compared with established RA patients, and to evaluate the risk factors for developing the OIs in the early stage of RA.

Methods Retrospective cohorts of early and established RA patients were conducted independently using the Korean National Healthcare claims database. Early RA patients (n=14,081) were identified in 2010 having disease free period for 1 year before index date, and receiving continuous treatment for over three years. Established RA patients (n=226,838) were recruited between 2010 and 2012 with using the ICD10 code of RA and any DMARD use. Follow-up started on the index date and ended on the data of the development of OIs, at 12 months, or at the time of death. The incidence rates of OIs were compared between two groups by calculating incidence rates ratio (IRR) and standardized incidence ratio (SIR) for overall or each OIs. The multivariable regression model was used to evaluate the risk factors for OIs in the early stage of RA.

Results The IRs of overall OI in early and established RA patients were 3.81 (95% CI 3.52–4.11)/100PY and 3.67 (95% CI, 3.59–3.74)/100PY, respectively. The SIR for overall OIs in early RA patients was 1.14 (95% CI, 1.05–1.23). The herpes zoster (SIR 1.12, 95% CI 1.03–1.22) and candidiasis (SIR 2.40; 95% CI 1.55–3.54) were commonly affected in the early stage of RA patients. Older age more than 50 years old [50<age≤60 (OR 1.74, 95% CI 1.30–2.33), 60<age≤70 (OR 1.85, 95% CI 1.36–2.52), 70<age (OR 1.89, 95% CI 1.34–2.68)], more comorbidities [one comorbidities (OR 1.53, 95% CI 1.24–1.89), ≥2 of comorbidities (OR 1.84, 95% CI 1.47–2.29)], and corticosteroid ≥5mg per day (OR 1.38, 95% CI 1.13–1.69) were associated with increased risk of OIs in the early stage of RA patients.

Conclusions The incidence of OIs is increased in early stage of RA patients compared with established RA patients. Old age, comorbidities, high corticosteroid dose were related with the development of OI. Physicians should be aware of the possible occurrence of OIs in early stage of RA treatment.

Disclosure of Interest None declared