The Disease Progression of Chinese Axial Spondyloarthritis in a Real-word Cohort Study

This is an observational cohort study of Chinese patients (≥18 years of age) diagnosed with axSpA. Patients are followed at 4-6 month intervals. Data will be collected at baseline and at every follow-up time points. Primary outcomes are the structural damage measured with imaging(Conventional radiography, low-dose CT and MRI) and the disease activity measured with the Ankylosing Spondylitis Disease Activity Scale (ASDAS) and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI). Secondary outcomes are inflammatory markers, Bath ankylosing spondylitis functional index (BASFI) and Bath ankylosing spondylitis metrology index (BASMI).

Primary outcomes

• BASFI [From enrollment to 16 weeks, 28 weeks, 1 year; after 1year on a an average of 6 months until study completion.]: The Bath Ankylosing Spondylitis Functional Index (BASFI) is a self-administered instrument comprising 10 items. The first 8 items assess functional activities (e.g., bending, reaching, climbing), while items 9 and 10 assess the patient's ability to cope with daily life and the impact of morning stiffness, respectively. Each item is scored on a 10 cm visual analog scale (or numerical rating scale), and the final score is the mean of the 10 items, ranging from 0 (best function) to 10 (worst function)
• Modified stoke ankylosing spondylitis spinal score (mSASSS) [2-year interval]: The mSASSS is a valid and widely used method for assessing radiographic progression in AS, correlating with worsening measures of disease signs and symptoms, spinal mobility and physical function.
• Anterior uveitis [From enrollment to 16 weeks, 28 weeks, 1 year; after 1year on a an average of 6 months until study completion.]: The occurrence of anterior uveitis episodes during the disease course in patients with axSpA

Secondary outcomes

• ASDAS-CRP [From enrollment to 16 weeks, 28 weeks, 1 year; after 1year on a an average of 6 months until study completion.]: ASDAS-CRP=0.12 x back pain+0.06 x duration of morning stifness +0.11 x patient global+0.07 x peripheral pain/swelling +0.58xIn(CRP+1) The result of the calculation is the ASDAS-CRP score, which is used to classify the disease activity level. Generally, a score of <1.3 indicates inactive disease, 1.3 - 2.1 indicates low disease activity, 2.1 - 3.5 indicates moderate disease activity, and >3.5 indicates high disease activity.
• ASDAS-ESR [From enrollment to 16 weeks, 28 weeks, 1 year; after 1year on a an average of 6 months until study completion.]: ASDAS-ESR=0.08 x back pain +0.07 x duration of morning stiffness + 0.11 x patient global + 0.09 x peripheral pain/swelling +0.29x√(ESR) The calculated score is used to determine the disease activity level. Typically, a score of <1.3 suggests inactive disease, 1.3 - 2.1 indicates low disease activity, 2.1 - 3.5 represents moderate disease activity, and >3.5 means high disease activity.
• BASDAI [From enrollment to 16 weeks, 28 weeks, 1 year; after 1year on a an average of 6 months until study completion.]: BASDAI is a validated self assessment tool used to determine disease activity i. Utilizing a Visual Analog Scale (VAS) of 0-10 (0=none and 10=very severe) participant's answered 6 questions measuring discomfort, pain and fatigue. The final BASDAI score averages the individual assessments for a final score range of 0-10.
• BASMI [From enrollment to 16 weeks, 28 weeks, 1 year; after 1year on a an average of 6 months until study completion.]: The Bath Ankylosing Spondylitis Metrology Index (BASMI) is a composite index derived from five clinical measurements of spinal and hip mobility: cervical rotation, tragus-to-wall distance, lumbar side flexion, lumbar flexion (modified Schober), and intermalleolar distance . Each component is scored on a scale from 0 to 10, and the total score (0-10, with 10 indicating the most severe impairment) is the mean of these five scores.
• The Spondyloarthritis Research Consortium of Canada (SPARCC) scoring system. [From enrollment to 16 weeks，1 year; after 1year on a an average of 6 months until study completion.]: The Spondyloarthritis Research Consortium of Canada (SPARCC) developers have created the SPARCC MRI scoring methods to assess inflammatory activity in patients with SpA.

Other outcomes

• CT Syndesmophyte Score [2-year interval]: The CT Syndesmophyte Score (CTSS) was developed for the assessment of syndesmophytes on LDCT images.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Patients aged 18 years or older
* Diagnosis of axial spondyloarthritis (axSpA) according to the Assessment of Spondyloarthritis International Society (ASAS) classification criteria

Exclusion Criteria:

* Presence of severe, unstable medical conditions that may interfere with the study assessments, including but not limited to:

End-stage renal disease (eGFR < 30 mL/min/1.73m²) Severe cardiovascular disease Active malignancy or malignancy requiring ongoing treatment

* Current diagnosis of schizophrenia, other psychotic disorders, severe cognitive impairment, or epilepsy with recurrent uncontrolled seizures, which, in the opinion of the investigator, may impair the ability to provide informed consent or comply with follow-up visits.
* Pregnant or lactating women