title: The B7 cross reactive group and spondyloarthropathies: an epidemiological approach.
abstract: OBJECTIVE
  To study the association between the B7 cross reactive group (B7, B40) and spondyloarthropathy (SpA), taking into account patients with atypical features.
  
  
  METHODS
  We studied the main clinical and paraclinical features of 51 patients with rheumatoid arthritis, 55 with SpA, 120 with mechanical diseases, and 160 with inflammatory rheumatism not fulfilling the diagnostic criteria currently used. This descriptive analysis was performed using multiple correspondence factorial analysis to identify subgroups among unclassified patients and select SpA variants. We compared HLA frequencies among these groups versus a control group.
  
  
  RESULTS
  We identified a subgroup close to the axial SpA and related to B7 (OR:5.91, p = 0.0008), whereas B40 is related to patients close to the peripheral SpA.
  
  
  CONCLUSIONS
  B7 is related to axial SpA variants manifested by inflammatory low back pain according to Calin's criteria, with either extraarticular signs or sacroiliitis. Followup of such patients is required to determine whether their disease is a new entity or can be considered SpA.
authors.affiliation: Rheumatology Service, Centre Hospitalier Universitaire de Besançon, France.
authors.forename: J P
authors.initials: JP
authors.lastname: Cedoz
authors.forename: D
authors.initials: D
authors.lastname: Wendling
authors.forename: J F
authors.initials: JF
authors.lastname: Viel
mesh_terms: D000328:Adult; D001172:Arthritis, Rheumatoid / Q000276:immunology; D001416:Back Pain / Q000209:etiology; D003429:Cross Reactions; D004812:Epidemiologic Methods; D005163:Factor Analysis, Statistical; D005260:Female; D015793:HLA-B7 Antigen / Q000276:immunology*; D006801:Humans; D008297:Male; D016017:Odds Ratio; D012216:Rheumatic Diseases / Q000276:immunology; D013122:Spinal Diseases / Q000150:complications / Q000276:immunology*
chemical_list: D015793:HLA-B7 Antigen