Objective: To investigate risk factors and characteristics of active tuberculosis (TB) in biologics-naïve rheumatoid arthritis (RA) patients.
Methods: Population-based case-control study using the Swedish Rheumatology Quality Register, the National Patient Register and the Tuberculosis Register to identify RA cases with active TB and matched RA controls without TB 2001-2014. Clinical data were obtained from medical records. TB risk was estimated as adjusted (adj) odds ratios (OR) with 95% confidence intervals (CI) using univariate and multivariable logistic regression analyses.
Results: After validation of diagnoses, the study included 31 RA cases with TB, and 122 matched RA controls. All except three cases had reactivation of latent TB. Pulmonary TB dominated (84%). Ever use of methotrexate was not associated with increased TB risk (adj OR 0.8; 95% CI 0.3-2.0), whereas ever treatment with leflunomide (adj OR 6.0; 95% CI 1.5-24.6), azathioprine (adj OR 3.8; 95% CI 1.1-13.8) and prednisolone (adj OR 2.4 (95% CI 1.0-5.9) was. There were no significant differences of maximum dose of prednisolone, treatment duration with prednisolone before TB, or cumulative dose of prednisolone the year before TB diagnosis between cases and controls. Obstructive pulmonary disease was associated with an increased TB risk (adj OR 3.9; 95% CI 1.4-10.7).
Conclusion: Several RA-associated factors may contribute to the increased TB risk in biologics-naïve RA patients, making risk of TB activation difficult to predict in the individual patient. To further decrease TB in RA patients, the results suggest that screening for latent TB should also be considered in biologics-naïve patients.