Background/Purpose: The ChinaAS is a nationwide, multicenter registry of patients with axial spondyloarthritis (SpA) in China to facilitate research in epidemiology, pathogenesis, diagnosis and treatment of Chinese patients with axial SpA.  The objective of this study is to describe the clinical manifestation of patients registered between July 11^th, 2018 and July 10^th, 2019, and compare the characteristics of patients who fulfill ASAS criteria and patients who fulfill modified New York criteria for ankylosing spondylitis (AS).

Methods: Patients with a clinical diagnosis of AS or axial SpA were enrolled into the registry from 31 provinces in China.  Demographics, clinical manifestations, HLA-B27 status, acute phase reactants, pelvis imagings, patient reported outcomes, medication use, and comorbidities were collected at baseline.  Patients, who were enrolled between July 11^th,2018 and July 10^th, 2019, and fulfilled either ASAS axial SpA criteria or modified New York criteria for AS, were included in the study.  Disease duration was defined as the difference between age of diagnosis and age of onset.  Early axial SpA was defined as disease duration of less than 3 years.  Descriptive statistics were used to described clinical characteristics of enrolled patients.

Results: A total of 3806 patients were included in the current analysis, including 3545 patients who fulfill modified New York criteria for AS, 3241 patients who fulfill ASAS criteria for axial SpA, and 3116 patients who fulfill ASAS criteria for axial SpA imaging arm.  Mean age at enrollment was 33 years, 73% were male, about 80% were HLA-B27 positive, and median disease duration was 4 years (Table 1).  Among these patients, 2384 patients had complete set of HLA-B27, baseline pelvis radiograph or CT, and baseline pelvis MRI.  Nineteen hundred and forty two patients had radiographic axial SpA, with 98% also fulfilled AS criteria (Figure 1).  In patients with early SpA (N = 924), majority (N=861, 93.2%) had sacroiliitis on pelvis radiograph or CT, 37 patients (4.0%) had sacroiliitis on MRI but not on pelvis radiograph or CT, and 26 patients (2.8%) were in the clinical arm without sacroiliitis on imaging studies.

Conclusion: In the ChinaAS registry, 3806 axial SpA patients were enrolled from July 11th, 2018 and July 10th, 2019.  Majority of patients (98%) with radiographic axial SpA also fulfilled modified New York criteria for AS.  In early axial SpA patients, more than 90% of them had a sacroiliitis on pelvis radiograph or CT.

Table 1. Baseline characteristics of patients in the ChinaAS registry. SD: standard deviation; IBD: inflammatory bowel disease; hsCRP: high sensitivity C-reactive protein; BASDAI: Bath ankylosing spondylitis disease activity index; BASFI: Bath ankylosing spondylitis functional index; ASDAS: ankylosing spondylitis disease activity score.

Figure 1. Venn diagram of ankylosing spondylitis and radiographic axial spondyloarthritis in patients with complete sets of HLA-B27, pelvis radiograph/CT and pelvis MRI.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-characteristics-of-patients-with-axial-spondyloarthritis-in-china-results-from-the-chinaas-registry/