The Effect of Prednisone on Tuberculin Skin Test Reaction in Patients with Rheumatoid Arthritis

Objectives. To assess the correlation between prednisone and methotrexate (MTX) treatment duration and dosage with the TST induration diameter of the TST reaction among rheumatoid arthritis (RA) patients. Method. We retrospectively analyzed consecutive cases of RA patients who were TNF-i therapy candidates. TST measurements, prednisone and methotrexate dosages, and treatment durations were recorded. A control group was randomly selected from healthy subjects. We compared TST reaction size between the following three groups: RA patients with current prednisone treatment, RA prednisone naïve patients, and healthy individuals. Results. Our study sample comprised 43 RA patients with prednisone treatment, 22 prednisone naïve patients, and 195 healthy subjects. There was no significant difference in mean TST between the groups (5.3±6.6, 7.8±6.2, and 7.6±7.0, respectively, p=0.149). No correlation was noted between TST size and prednisone u-y (r=0.229, p=0.140) or methotrexate u-y in patients with and without prednisone therapy (r=0.219, p=0.158; and r=-0.293, p=0.186, respectively). Conclusions. Our results show that the TST reaction size among RA patients may not be affected by prednisone therapy. In addition, the TST reaction of RA patients may present similarly to that of healthy individuals. Therefore, we suggest that the criterion of a TST reaction of 5 mm to define latent TB infection in our population should be reevaluated.