Background Diagnosis and differential diagnosis of various forms of spondyloarthritides is primarily based on the clinical manifestations and radiographic features analysis. Clinical manifestations though can be quite similar, so imaging studies data play an important role in diagnosis.

Objectives To evaluate the differences of certain forms of spondyloarthritides in terms of radiographic features and also the opportunity to establish differential diagnosis and prognosis of the disease on this basis.

Methods The study enrolled 100 patients with spondyloarthritides. The first arm included 50 patients with ankylosing spondylitis (AS). The second arm included 50 patients with Chlamydia-induced spondyloarthritis (HiSPA). The diagnosis of AS was made on the basis of the modified New York criteria (1984). Mean patients' age was 34.0±10.9 years in the AS arm and 27.1±6.9 years in the HiSPA arm. All patients in both arms were males. Mean disease duration was 6.4±4.5 years [1.9; 10.9] in the AS arm and 5.6±4.7 years [0.9; 10.3] in the HiSPA arm. Patients underwent radiography of the sacroiliac joints (SIJ), lumbar, thoracic and cervical spine. We evaluated and compared the frequency of the following radiographic features: erosions/pseudodilation or irregular narrowing of the SIJ, SIJ ankylosis, symmetrical syndesmophytes in any region of the spine, asymmetrical syndesmophytes in any region of the spine.

Results Our study showed the following rate of the individual radiographic features: erosions/pseudodilation or irregular narrowing of the SIJ: 11 (22.0%) in the first arm and 32 (64.0%) in the second arm (p<0.05); SIJ ankylosis: 28 (56.0%) in the first arm and 2 (4%) in the second arm (p<0.05); symmetrical syndesmophytes: 34 (68%) in the first arm and 3 (6.0%) in the second arm; asymmetrical syndesmophytes: 5 (10.0%) in the first arm and 21 (42.0%) in the second arm (p<0.05). Furthermore, in the AS arm radiography significantly more often revealed simultaneous involvement of all 3 spine regions (cervical, thoracic, lumbar): 17 (34.0%) vs. 2 (4.0%) in the HiSPA arm (p<0,05).

Thus, despite the general similarity of radiographic features, we have identified significant differences, which, in our opinion, are due to diversity of pathogenesis and can be considered predictors of structural disease progression rate. This observation can help in the diagnosis and disease prognosis establishment, as well as in the prediction of the skeletal dysfunction course in patients with spondyloarthritides.

Conclusions Our findings suggest differences in AS and HiSPA radiographic features. In the first arm they were of more pronounced proliferative and progressive nature, and in the second had distinct inflammatory features with less progression while disease duration in both groups was quite comparable.

Disclosure of Interest None declared