Chronic pain and assessment of pain sensitivity in patients with axial spondyloarthritis: Results from the SPARTAKUS cohort

Objective To study differences in pain reports between patients with ankylosing spondylitis (AS) and non-radiographic axial spondyloarthritis (nr-axSpA), and to assess how pain sensitivity measures associate with disease and health outcomes.

Methods Consecutive patients with axial SpA (axSpA) were enrolled in the populationbased SPARTAKUS cohort (2015‒2017), and classified as AS (n=120) or nr-axSpA (n=55). Pain was assessed with questionnaires (intensity/duration/distribution) and computerized cuff pressure algometry to measure pain sensitivity (pain threshold/pain tolerance/temporal summation of pain). Linear regression models were used to compare pain measures between AS and nr-axSpA patients, and to assess associations between pain sensitivity measures and disease and health outcomes.

Results Of 175 axSpA patients, 44% reported chronic widespread pain, with no significant differences in any questionnaire-derived or algometry-assessed pain measures between AS and nr-axSpA patients. Lower pain tolerance was associated with longer symptom duration, worse ASDAS-CRP, BASFI, and BASMI, more pain regions, unacceptable pain, worse MASES, fatigue, anxiety, and health-related quality of life. Furthermore, lower pain threshold was associated with worse ASDAS-CRP and MASES, while higher temporal summation was associated with longer symptom duration, unacceptable pain and worse BASMI.

Conclusion Chronic pain is common in axSpA, with no observed differences in any pain measures between patients with AS and nr-axSpA. Furthermore, higher pain sensitivity is associated with having worse disease and health outcomes. The results indicate that patients with AS and nr-axSpA, in line with most clinical characteristics, have a similar pain burden and they highlight large unmet needs regarding individualized pain management, regardless of axSpA subgroup.