title: Functional limitations due to axial and peripheral joint impairments in patients with ankylosing spondylitis: are focused measures more informative?
abstract: OBJECTIVE
  Functional limitations in ankylosing spondylitis (AS) may be due to peripheral joint or axial involvement. To determine if the Bath Ankylosing Spondylitis Functional Index (BASFI), an axial-focused measure, can detect limitations related to peripheral joint involvement equally as well as the Health Assessment Questionnaire modified for the spondyloarthropathies (HAQ-S), a peripheral arthritis-focused measure, and vice versa, we compared associations of each questionnaire with spinal and hip range of motion, peripheral arthritis, and enthesitis in patients with AS.
  
  
  METHODS
  We examined patients every 4-6 months in this prospective longitudinal study. We used mixed linear models to analyze the associations between 10 physical examination measures and the BASFI and HAQ-S.
  
  
  RESULTS
  We studied 411 patients for a median of 1.5 years (median 3 visits). In multivariate analyses, cervical rotation, chest expansion, lateral thoracolumbar flexion, hip motion, tender joint count, and tender enthesis count were equally strongly associated with the BASFI and HAQ-S. Peripheral joint swelling was more strongly associated with the HAQ-S. Individual items of the BASFI were more likely than items of the HAQ-S to be associated with unrelated physical examination measures (e.g., the association between difficulty rising from a chair and cervical rotation), which may have diminished the axial/peripheral distinction for the BASFI.
  
  
  CONCLUSIONS
  The BASFI and HAQ-S had similar associations with impairments in axial measures, while the HAQ-S had stronger associations with the number of swollen peripheral joints. The HAQ-S should be considered for use in studies focused on spondyloarthritis with peripheral joint involvement.
authors.affiliation: National Institute of Arthritis and Musculoskeletal and Skin Diseases, NIH, Bethesda, Maryland 20892-1468, USA.
authors.forename: Siddharth
authors.initials: S
authors.lastname: Bethi
authors.forename: Abhijit
authors.initials: A
authors.lastname: Dasgupta
authors.forename: Michael H
authors.initials: MH
authors.lastname: Weisman
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Learch
authors.forename: Lianne S
authors.initials: LS
authors.lastname: Gensler
authors.forename: John C
authors.initials: JC
authors.lastname: Davis
authors.forename: John D
authors.initials: JD
authors.lastname: Reveille
authors.forename: Michael M
authors.initials: MM
authors.lastname: Ward
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D004185:Disability Evaluation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007596:Joints / Q000503:physiopathology*; D008297:Male; D010147:Pain Measurement / Q000379:methods*; D011446:Prospective Studies; D016059:Range of Motion, Articular; D012720:Severity of Illness Index; D013167:Spondylitis, Ankylosing / Q000175:diagnosis / Q000503:physiopathology / Q000534:rehabilitation*; D011795:Surveys and Questionnaires