To determine factors associated with development, recurrence, and severity of infections in patients with rheumatoid arthritis (RA).
A hospital based nested case-control study in a referral center. The same evaluator reviewed clinical charts of 195 consecutive patients with RA seen in our clinic during 1993. Patients who had had at least one infection were classified as "cases" and the others as "controls." We examined 24 demographic, clinical, therapeutic, and infection related variables. A severity index was developed according to scores provided by 12 independent multidisciplinary evaluators. Recurrent infection was defined as > 2 different infections in the same patient during followup. Descriptive statistics were employed, with comparison between cases and controls by univariate analysis and multiple logistic regression.
Two hundred eleven infections were detected in 1274 patient-years (incidence of 0.17 new infections per patient-year). We studied 174 women and 21 men, mean 41 years of age, with a mean duration of symptoms of RA of 5 years. Ninety-five were cases and 100 controls. Cases had longer disease duration before admission and followup (p < 0.05). Infections most commonly seen were upper respiratory tract (n = 74), skin (41), urinary tract (27), and herpes zoster (15). Steroids and/or methotrexate (MTX) were associated in 95% of infections. Infection was associated with duration of RA before admission and followup, comorbidity, extraarticular disease, mean cumulative dose of MTX, time taking steroids, and mean daily dose of D-penicillamine, by univariate analysis. Severity of infection was related to the same variables and years of formal education, and recurrence of infection was related to time of followup and mean dose of MTX and steroids. Multiple logistic regression showed that variables associated with infection were cumulative MTX dose, time taking steroids, and mean daily dose of D-penicillamine.
Infections were frequent in our RA population. The risk factors associated with infections were the cumulative dose of MTX, duration taking steroids, and mean daily dose of D-penicillamine.