Clinical characteristics of axial spondyloarthritis patients in China: results from ChinaSpA, the Chinese Spondyloarthritis Registry

Objective The objective of this study is to describe the clinical features of patients with axial spondyloarthritis (axial SpA) in the ChinaSpA registry. Methods Patients with clinical diagnosis of ankylosing spondylitis (AS) or axial SpA were enrolled into the registry. Patients with a complete set of pelvis radiograph, pelvis MRI and HLA-B27 (Complete Set group, CS group) were further categorised based on classification criteria into AS, radiographic axial SpA (r-axSpA) and non-radiographic axial SpA (nr-axSpA). Early axial SpA was defined as symptom duration of less than three years. Descriptive statistics were used to describe clinical characteristics of enrolled patients. ANOVA analyses were used to compare patients in different groups. Results A total of 5270 patients were enrolled in the study, and 3223 patients had complete sets of pelvis radiographs, MRIs and HLA-B27 status. Among them, more than 80% patients met both the ASAS criteria for r-axSpA and the modified New York criteria for AS. Among those with early axial SpA, 92% of patients had sacroiliitis on pelvis radiograph, 3.8% had sacroiliitis only on pelvis MRI, and 3.8% were in the clinical arm without any sacroiliitis on imaging studies. Patients in nr-axSpA clinical arm had less diagnosis delay, lower inflammatory markers and ASDAS, compared to patients in the r-axSpA, nr-axSpA MRI arm. Conclusion In the ChinaSpA registry, patients in nr-axSpA clinical arm had the shortest diagnostic delay, lower inflammatory markers and ASDAS, but no difference in extra-articular manifestation, compared to patients in the r-axSpA and nr-axSpA MRI arm.