title: Clinical features of axial undifferentiated spondyloarthritis (USpA) in China: HLA-B27 is more useful for classification than MRI of the sacroiliac joint.
abstract: OBJECTIVE
  To analyse the clinical features of Chinese undifferentiated spondyloarthritis (USpA) patients with predominantly axial involvement, and in particular the influence of human leucocyte antigen (HLA)-B27 and magnetic resonance imaging (MRI) of the sacroiliac joint (SIJ) on the classification of axial USpA.
  
  
  METHODS
  Patients with low back pain for ≥ 3 months and no definite radiographic sacroiliitis were enrolled in this study. They were diagnosed as USpA based on rheumatologists' findings. Correlations between clinical features and HLA-B27 status or MRI manifestations were analysed.
  
  
  RESULTS
  A total of 197 USpA patients were recruited, of whom 135 (70.3%) were positive for HLA-B27. Acute inflammation, structural damage lesions, and normal findings on SIJ MRI were recorded in 64.5, 13.2 and 22.3% of patients, respectively. Classification criteria for axial SpA according to the European Spondylarthropathy Study Group (ESSG), Amor, and the Assessment of SpondyloArthritis International Society (ASAS) were fulfilled by 63.5, 64.5 and 83.2% patients, respectively. Cross-validation showed significant correlation among these three criteria. Patients positive for HLA-B27 included more males, with earlier onset age, better response to non-steroidal anti-inflammatory drugs (NSAIDs), and higher erythrocyte sedimentation rate (ESR)/C-reactive protein (CRP) levels. In addition, more HLA-B27-positive than HLA-B27-negative patients fulfilled the ESSG, Amor, and ASAS criteria. Patients with acute inflammation on SIJ MRI had a higher level of ESR/CRP, and a greater proportion of them fulfilled the Amor and ASAS criteria. However, the proportion of those fulfilling the ESSG criteria did not differ with different MRI manifestations.
  
  
  CONCLUSIONS
  Both HLA-B27 status and SIJ MRI findings influence the classification of Chinese axial USpA patients, but HLA-B27 seems of more value.
authors: Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China.
authors: Z
authors: Z
authors: Liao
authors: Z
authors: Z
authors: Lin
authors: M
authors: M
authors: Xu
authors: Z
authors: Z
authors: Hu
authors: T
authors: T
authors: Li
authors: Q
authors: Q
authors: Wei
authors: S
authors: S
authors: Cao
authors: J
authors: J
authors: Huang
authors: Y
authors: Y
authors: Pan
authors: Y
authors: Y
authors: Wu
authors: J
authors: J
authors: Gu
mesh_terms: D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000097:blood*; D002681:China; D005260:Female; D015796:HLA-B27 Antigen / Q000097:blood*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012446:Sacroiliac Joint / Q000473:pathology*; D025241:Spondylarthritis / Q000145:classification / Q000175:diagnosis* / Q000276:immunology; D055815:Young Adult
chemical_list: D015415:Biomarkers; D015796:HLA-B27 Antigen