[Combined comorbid pathology in axial spondyloarthritis]

To analyze the frequency of combined comorbid pathology and its effect on clinical and instrumental characteristics in axial spondyloarthritis (SpA), including axial psoriatic arthritis.

222 patients were included in the study: 108 with axial SpA, 114 with axial psoriatic arthritis. The average age was 40.9±12.4 years, and the duration of inflammatory back pain was 68±53.3 months. A standard rheumatological examination, X-ray of the cervical and lumbar spine, and pelvis were performed. The activity of spondylitis was determined by BASDAI and ASDAS-CRP. The patients were divided into 3 groups: 1st - without comorbid diseases (CD) - 66 (29.7%) patients, 2nd - with 1-2 CD - 78 (35.1%), 3rd - with ≥3 CD - 78 (35.1%).

The patients in 3rd group were older than in the other groups (in 1st group - 39±12.1 years, in 2nd - 39±11.2, in 3rd - 44.5±13.1; p_1-3=0.039, p_2-3=0.028), they had a higher level of Pain (in the 1st - 54.3±19.7 mm VAS, in the 2nd - 51.1±22.7, in the 3rd - 63.3±19.4; p=0.01 for all comparisons), the ASDAS-CRP value was higher than in the 1st group (in the 1st - 2.2±1.1, in the 2nd - 2.6±1.1, 3rd - 2.7±0.9; p_1-3=0.01), syndesmophytes were more common in the cervical and/or lumbar spine, ankylosis of the faceted joints in the cervical spine (p< 0.05). The results of the cluster analysis allowed us to group the features into 4 main clusters. The first cluster, in which the ASDAS-CRP and BASDAI indices were grouped, is combined, on the one hand, with a cluster with the presence of psoriasis, comorbidity (≥3), and structural changes in the spine, on the other hand, with other CD and extra-skeletal manifestations of SpA.

The presence of a combination of CD was associated with higher activity of spondylitis, more common structural injuries of the spine. The choice of therapy, taking into account СD and extra-skeletal manifestations of SpA, should improve patient treatment outcomes.