Clinically relevant deficits in performance tests in patients with axial spondyloarthritis

Objective. To assess the association between self-reported and performance-based physical functioning and to evaluate which performance tests are most frequently impaired in patients with axial spondyloarthritis (axSpA).Methods. Consecutive patients with axSpA underwent standardized assessments including patient and disease characteristics; patient-reported outcomes for disease activity, functioning, depression, mobility, and physical activity; and performance tests. Patients were defined as being impaired if they were not able to perform >= 1 of the performance tests. Validated cut-offs were used to define impaired physical performance. Impairment of performance tests as well as discrimination between subgroups were analyzed.Results. A total of 200 patients (radiographic axSpA 66.5%, nonradiographic axSpA 33.5%) were included: 69% males, mean age 44.3 (SD 12.5) years, and mean symptom duration 17.9 (SD 12.6) years. The 2 most frequently impaired performance tests were the repeated chair stand test (n = 75, 37.5%) and putting on socks (n = 44, 22%). An impairment in >= 1 performance test was seen in 91 patients (45.5%). Patients with impairments were older (49.1 yrs vs 40.3 yrs); had a higher BMI (28.9 kg/m2 vs 25.8 kg/m2); a more active disease (Ankylosing Spondylitis Disease Activity Score, 3.0 vs 2.1); higher Bath Ankylosing Spondylitis Functional Index (BASFI; 5.8 vs 2.7), Bath Ankylosing Spondylitis Metrology Index (BASMI; 4.4 vs 2.7), and Assessment of Spondyloarthritis international Society Health Index scores (9.5 vs 4.9); and higher depression screen values (9-item Patient Health Questionnaire, 11.6 vs 6.5; all P < 0.01).Conclusion. Many patients with axSpA had impairments in physical performance tests. Importantly, this was frequently seen in tasks requiring coordination and muscle power of the lower extremity. Performance tests provide qualitatively different information than BASFI and BASMI assessments in patients with axSpA.