The results of purified protein derivative test in ankylosing spondylitis patients: clinical features, HRCT results and relationship with TNF-blocker usage

In this study, we evaluated the clinical features, treatment modalities, including TNF-blockers, purified protein derivative (PPD) test, chest X-ray and HRCT results in our AS patients. We evaluated the clinical features, disease activity and PPD results in 88 AS patients (72 males, 16 females, mean age: 38.3 ± 10) diagnosed at our center. 119 RA, 28 SLE and 27 gouty arthritis patients followed up at the same time period were taken as the control group. The mean disease duration in AS patients was 12.6 ± 8.3 years. The frequency of PPD positivity in AS patients (77.3%) was similar to that in gouty arthritis (70.4%) patients; and significantly higher than the frequency in SLE (21.4%) and RA (35.3%) patients (P values <0.001). There was a chest X-ray abnormality in 20 AS patients (22.7%). When subjects (11 patients, 12.5%) with apical fibrosis, aspergillosis, previous or active TB on chest X-ray and/or HRCT were compared to others; it was observed that they were older (P < 0.001), had longer disease duration (P = 0.006); and less chest expansion (P = 0.01). Fifty patients were administered TNF-blockers. The PPD test was positive in 38 of patients (76%) using TNF-blockers. All of these patients were given isoniazid prophylaxis. After a median follow up of 18 months, TB did not develop. In Turkey which is a country with a relatively high incidence of TB, in spite of a higher frequency of PPD positivity in AS patients compared to RA and SLE patients, TNF-blockers did not result in any TB with suitable prophylaxis.