title: The discriminative value of inflammatory back pain in patients with persistent low back pain.
abstract: OBJECTIVE
  To estimate the prevalence of inflammatory back pain (IBP) characteristics and analyse the discriminative value of IBP relative to axial spondyloarthritis (SpA) according to the Assessment of SpondyloArthritis international Society (ASAS) criteria.
  
  
  METHODS
  Patients who had low back pain for > 3 months were selected from a cohort of secondary care patients aged 18-40 years. Data included information on SpA features, human leucocyte antigen (HLA)-B27 typing, C-reactive protein (CRP) level, magnetic resonance imaging (MRI) of the sacroiliac joints, and self-reported IBP questions covering the pain characteristics included in the Calin, Berlin, and ASAS IBP definitions.
  
  
  RESULTS
  Of the 759 included patients, 99% [95% confidence interval (CI) 98-100] had at least one IBP characteristic. The prevalence of the single IBP characteristics ranged from 10% (95% CI 7-12) for 'pain worst in the morning' to 79% (95% CI 76-82) for 'morning stiffness'. Two-thirds of the patients (67%, 95% CI 63-70), met at least one of the three IBP definitions. In all, 86 (11%) were classified as 'SpA according to ASAS'. All three IBP definitions were significantly associated with 'SpA according to ASAS'; however, the discriminative value was low, with sensitivity, specificity, and balanced accuracy values of 64, 50, and 57% for Calin, 59, 60, and 60% for Berlin, and 35, 79, and 57% for ASAS IBP definitions, respectively.
  
  
  CONCLUSIONS
  In this study population, IBP characteristics were in general common and the discriminative value was low, as IBP could not differentiate patients with SpA according to ASAS criteria from patients with other causes of back pain.
authors.affiliation: a Research Department, Spine Centre of Southern Denmark , Hospital Lillebaelt , Middelfart , Denmark.|b Institute of Regional Health Research , University of Southern Denmark , Odense , Denmark.
authors.forename: B
authors.initials: B
authors.lastname: Arnbak
authors.affiliation: b Institute of Regional Health Research , University of Southern Denmark , Odense , Denmark.|c King Christian X Hospital for Rheumatic Diseases , Graasten , Denmark.
authors.forename: O
authors.initials: O
authors.lastname: Hendricks
authors.affiliation: b Institute of Regional Health Research , University of Southern Denmark , Odense , Denmark.|c King Christian X Hospital for Rheumatic Diseases , Graasten , Denmark.
authors.forename: K
authors.initials: K
authors.lastname: Hørslev-Petersen
authors.affiliation: a Research Department, Spine Centre of Southern Denmark , Hospital Lillebaelt , Middelfart , Denmark.|b Institute of Regional Health Research , University of Southern Denmark , Odense , Denmark.|d Department of Radiology , Aarhus University Hospital , Aarhus , Denmark.
authors.forename: A G
authors.initials: AG
authors.lastname: Jurik
authors.affiliation: e Copenhagen Centre for Arthritis Research , Centre for Rheumatology and Spine Diseases , Glostrup , Denmark.|f Department of Clinical Medicine , University of Copenhagen , Copenhagen , Denmark.
authors.forename: S J
authors.initials: SJ
authors.lastname: Pedersen
authors.affiliation: e Copenhagen Centre for Arthritis Research , Centre for Rheumatology and Spine Diseases , Glostrup , Denmark.|f Department of Clinical Medicine , University of Copenhagen , Copenhagen , Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Østergaard
authors.affiliation: b Institute of Regional Health Research , University of Southern Denmark , Odense , Denmark.|c King Christian X Hospital for Rheumatic Diseases , Graasten , Denmark.
authors.forename: L T
authors.initials: LT
authors.lastname: Hermansen
authors.affiliation: g Department of Medicine , Hospital Lillebaelt , Vejle , Denmark.|h Department of Rheumatology , Aarhus University Hospital , Aarhus , Denmark.
authors.forename: A G
authors.initials: AG
authors.lastname: Loft
authors.affiliation: a Research Department, Spine Centre of Southern Denmark , Hospital Lillebaelt , Middelfart , Denmark.|b Institute of Regional Health Research , University of Southern Denmark , Odense , Denmark.
authors.forename: T S
authors.initials: TS
authors.lastname: Jensen
authors.affiliation: a Research Department, Spine Centre of Southern Denmark , Hospital Lillebaelt , Middelfart , Denmark.|b Institute of Regional Health Research , University of Southern Denmark , Odense , Denmark.
authors.forename: C
authors.initials: C
authors.lastname: Manniche
mesh_terms: D000328:Adult; D002097:C-Reactive Protein / Q000276:immunology; D002940:Circadian Rhythm; D015331:Cohort Studies; D005260:Female; D015796:HLA-B27 Antigen / Q000235:genetics; D006801:Humans; D007249:Inflammation; D017116:Low Back Pain / Q000175:diagnosis* / Q000276:immunology / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008297:Male; D012446:Sacroiliac Joint / Q000000981:diagnostic imaging*; D057566:Self Report; D012680:Sensitivity and Specificity; D025242:Spondylarthropathies / Q000175:diagnosis* / Q000235:genetics / Q000276:immunology / Q000503:physiopathology; D011795:Surveys and Questionnaires; D013997:Time Factors
chemical_list: D015796:HLA-B27 Antigen; D002097:C-Reactive Protein