Multicenter Validation of the 2025 Classification Criteria for Axial Spondyloarthritis

Overview

This study aims to validate the 2025 ASAS-SPARTAN revised classification criteria for axial spondyloarthritis (axSpA) in the Chinese population through a multicenter, prospective, cross-sectional observational study. Axial spondyloarthritis is a chronic inflammatory disease primarily affecting the spine and sacroiliac joints, causing back pain and stiffness. Early and accurate diagnosis is essential for timely treatment and improved patient outcomes. The 2025 ASAS-SPARTAN revised classification criteria were recently developed by the Assessment of SpondyloArthritis International Society (ASAS) and the SpondyloArthritis Research and Treatment Network (SPARTAN) to improve diagnostic accuracy and reduce over-diagnosis, with preset targets of sensitivity ≥75% and specificity ≥90%. However, the original validation study included only 71 Chinese patients out of 1,015 total participants, and racial differences in susceptibility genes, living environments, and socioeconomic-cultural backgrounds may affect the criteria's performance in Chinese patients. This study will enroll patients with chronic back pain (CBP) lasting ≥3 months and onset age ≤45 years from multiple hospitals in China. All participants will undergo comprehensive diagnostic assessments including clinical history, physical examination, CRP testing, HLA-B27 testing, pelvic X-ray, and sacroiliac joint MRI. The 2025 ASAS-SPARTAN criteria will be applied to evaluate diagnostic performance, and results will be compared with the 2009 ASAS classification criteria and clinicians' gold-standard diagnoses. The primary objective is to validate the sensitivity, specificity, and internal scoring rationality of the 2025 ASAS-SPARTAN criteria in Chinese axSpA patients. The secondary objective is to assess the concordance between the 2025 and 2009 ASAS criteria and analyze reasons for any discrepancies. The findings will provide evidence for Chinese clinicians to select appropriate classification tools, reduce over-diagnosis of axSpA, and alleviate the burden on the healthcare system.

Detailed description

This is a multicenter, observational, cross-sectional study conducted across 4 hospitals in China, led by the Department of Rheumatology and Immunology at Chinese PLA General Hospital (First Medical Center).

Study Design:

* Prospective enrollment of eligible patients over 12 months * No intervention; all diagnostic and treatment decisions are made by clinicians based on clinical judgment * Data collection through standardized electronic case report forms (eCRF) using EpiData platform

Study Population:

* Adults with chronic back pain (CBP) duration ≥3 months * Back pain onset age ≤45 years * Patients presenting to rheumatologists without confirmed diagnosis of axSpA, AS, or other rheumatic diseases * Patients willing to complete full diagnostic assessments and provide informed consent

Assessments:

* Clinical history and physical examination * Laboratory tests: complete blood count, liver and renal function, HLA-B27, ESR, CRP * Imaging: pelvic and whole-spine X-ray, sacroiliac joint MRI, sacroiliac joint CT; additional imaging (hip/spine MRI or CT, joint ultrasound, bone scan) as clinically indicated

Diagnostic Evaluation:

* Clinicians will establish a gold-standard diagnosis based on comprehensive clinical, laboratory, and imaging findings * Both 2025 ASAS-SPARTAN and 2009 ASAS classification criteria will be applied to each patient * Statistical analysis will evaluate sensitivity, specificity, and concordance between criteria

Sample Size: 247 patients (calculated using PASS 2021 software for one-sample sensitivity and specificity confidence intervals, based on expected sensitivity 75%, specificity 90%, and prevalence 0.7)

Statistical Methods:

* Continuous variables: mean ± standard deviation, independent sample t-test * Categorical variables: relative frequencies, Chi-square test * Multivariate logistic regression and Cox regression for prognostic factor analysis * P \< 0.05 considered statistically significant

Data Management:

* Standardized eCRF with defined variable definitions and coding rules * Password-protected online data entry platform * De-identification of personal information for publication and data sharing * Compliance with GCP, Declaration of Helsinki, and Chinese regulatory requirements

Interventions

• Other Diagnostic Assessment
  Comprehensive diagnostic evaluation including clinical history, physical examination, laboratory tests (CBC, liver/renal function, HLA-B27, ESR, CRP), and imaging studies (pelvic X-ray, sacroiliac joint MRI/CT). No therapeutic intervention is provided as part of this study; all diagnostic and treatment decisions are made by clinicians according to standard clinical practice

Primary outcome measures

• Diagnostic accuracy of the 2025 ASAS-SPARTAN classification criteria for axial spondyloarthritis [Time frame: At baseline (single assessment during index visit)]

Secondary outcome measures (1)

• Concordance between 2025 ASAS-SPARTAN and 2009 ASAS classification criteria [Time frame: At baseline (single assessment during index visit)]

Eligibility criteria

Inclusion criteria

• 1\. Presence of current chronic back pain with duration ≥3 months and without a definitive diagnosis 2. Age at onset of back pain ≤45 years 3. Presentation to a rheumatologist for evaluation of suspected axial spondyloarthritis or related conditions, without a confirmed diagnosis of axSpA or other rheumatic diseases 4. Willingness to complete comprehensive diagnostic assessments including clinical history, physical examination, CRP testing, HLA-B27 testing, pelvic X-ray, and sacroiliac joint MRI (recent imaging may be acceptable if completed within appropriate timeframe) 5. Voluntary participation with provision of signed electronic informed consent

Exclusion criteria

• 1\. Inability to communicate due to cognitive impairment, visual impairment, or other factors affecting self-assessment 2. Confirmed diagnosis of axial spondyloarthritis (axSpA), ankylosing spondylitis (AS), or other established rheumatic diseases (e.g., rheumatoid arthritis, psoriatic arthritis) 3. Back pain duration <3 months or age at onset >45 years 4. Refusal or inability to complete full diagnostic evaluation due to medical contraindications (e.g., metallic implants preventing MRI, severe hepatic or renal dysfunction precluding laboratory testing) 5. Presence of clearly identified non-SpA causes of chronic back pain with established diagnosis, including lumbar disc herniation, spinal stenosis, spinal tumors, infectious spondylitis, or osteoporotic fractures 6. Failure to provide informed consent, inability to cooperate with study follow-up, or inability to provide complete data

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Observational model

Other

Study locations

China · 1 center

• Chinese PLA General Hospital — Beijing

Publications

• Ez-Zaitouni Z, Bakker PAC, van Lunteren M, Berg IJ, Landewe R, van Oosterhout M, Lorenzin M, van der Heijde D, van Gaalen FA. Presence of multiple spondyloarthritis (SpA) features is important but not sufficient for a diagnosis of axial spondyloarthritis: data from the SPondyloArthritis Caught Early (SPACE) cohort. Ann Rheum Dis. 2017 Jun;76(6):1086-1092. doi: 10.1136/annrheumdis-2016-210119. Epub PMID 28062405

Identifiers

NCT: NCT07724847 · ChinaPLAGH-axSpA

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗