To quantify the risk of tuberculosis (TB) in an unselected sample of patients with rheumatoid arthritis (RA) compared to the risk in the general population.
The incidence of TB in the general population of Spain was obtained from the National Network of Epidemiological Surveillance reports. The incidence of TB was ascertained from a cohort of 788 patients with RA selected randomly from the registries of 34 participating centers throughout Spain. A patient was considered a TB case only if information about disease symptoms, microorganism identification, and TB treatment were confirmed in the clinical records. The relative risk of TB in RA was calculated by dividing the standardized mean incidence of TB from 1990 to 2000 in the RA cohort by the mean incidence of TB in Spain during the same years.
The mean incidence of TB in the general population of Spain from 1990 to 2000 was 23 cases per 100,000. Seven cases of TB were identified in the RA cohort, yielding a mean annual incidence (1990-2000) of 134/100,000 patients. The incidence risk ratio of pulmonary TB in patients with RA compared to the general population is 3.68 (95% CI 2.36-5.92).
We found a 4-fold increased risk of TB infection in patients diagnosed with RA. These results might help to interpret the magnitude of the problem attributable to the introduction of new therapies in RA.