In this study, we aimed to evaluate the frequency of purified protein derivative (PPD) skin test positivity and associated clinical features in RA patients.
We included 94 (80 F, 14 M, mean age: 55.8) consecutive RA patients with a disease duration of 8.7 years. PPD test was performed in all RA patients; clinical features were recorded down; chest x-ray, pulmonary function tests and HRCT were available in all cases. As the control group, we included data of 21 SLE, 44 AS, 27 OA, 16 gouty arthritis and 18 vasculitis patients.
The frequencies of PPD positivity in RA (29.8%) and SLE (19%) patients were lower than in patients with AS (65.9%), gouty arthritis (68.8%) and OA (63%) (all p values < 0.01). PPD-positive RA patients were more frequently smokers (p = 0.005) and had a higher rate of RF seropositivity (p = 0.04) than PPD-negatives. PPD was less frequently positive in erosive RA disease (p = 0.033). Chest x-rays and HRCT abnormalities were detected in 41.8% and 62.7% of RA patients, respectively. Frequencies of chest x-ray and HRCT abnormalities in PPD-positive and PPD-negative patients were not different from each other (p > 0.05).
In our country in which tuberculosis is relatively frequent -contrary to the situation in AS patients- we observed a lower frequency of PPD positivity in RA and SLE patients compared to patients with other rheumatic diseases. We did not find any relationship between PPD positivity and the frequency of chest x-ray, HRCT abnormalities.