title: Optimizing the identification of patients with axial spondyloarthritis in primary care--the case for a two-step strategy combining the most relevant clinical items with HLA B27.
abstract: OBJECTIVE
  The combination of clinical items suggestive of inflammatory back pain has proved useful for early identification of patients with axial SpA (axSpA) in primary care. However, whether HLA B27 contributes to that is unclear, and published recommendations have advised against it. In this study, we reanalysed data of that trial in relation to the HLA B27 results.
  
  
  METHODS
  Consecutive patients <45 years old (n = 950) with back pain (BP) >2 months presenting to 143 orthopaedists were referred to 36 rheumatologists who made the diagnosis. The predictive value of HLA B27 (n = 298) alone and in combination, including modelling and a two-step strategy, was calculated.
  
  
  RESULTS
  Among all patients (mean age 36 years, 52% female, median duration of BP 32 months), 107 had axSpA (36%). Using a simple model, HLA B27 alone performed better than all combinations of clinical items and adding it did not improve likelihood ratios (LRs). Using modelling, two-phase strategies were analysed. Additional items were only relevant in the HLA B27-negative group: improvement by movement, buttock pain and psoriasis. Combining this information revealed the presumably best strategy to predict axSpA in primary care: more than one of these items or HLA B27 need to be present (sensitivity 80.4%, specificity 75.4%, LR+ 3.27 and LR- 0.26).
  
  
  CONCLUSIONS
  This is the first study to show that patients with axSpA are more reliably identified in primary care by a strategy that includes HLA B27. Because of the two-step approach, the test needs to be performed in only about half of patients with chronic BP.
authors.affiliation: Rheumazentrum Ruhrgebiet, Landgrafenstrasse 15, 44652 Herne, Germany.
authors.forename: Annalina
authors.initials: A
authors.lastname: Braun
authors.forename: Holger
authors.initials: H
authors.lastname: Gnann
authors.forename: Ertan
authors.initials: E
authors.lastname: Saracbasi
authors.forename: Joachim
authors.initials: J
authors.lastname: Grifka
authors.forename: Uta
authors.initials: U
authors.lastname: Kiltz
authors.forename: Katrin
authors.initials: K
authors.lastname: Letschert
authors.forename: Jürgen
authors.initials: J
authors.lastname: Braun
mesh_terms: D000328:Adult; D000368:Aged; D001368:Axis, Cervical Vertebra / Q000473:pathology; D015415:Biomarkers / Q000032:analysis; D015331:Cohort Studies; D005260:Female; D015796:HLA-B27 Antigen / Q000032:analysis / Q000276:immunology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011320:Primary Health Care / Q000379:methods*; D011446:Prospective Studies; D012446:Sacroiliac Joint / Q000503:physiopathology; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D025241:Spondylarthritis / Q000175:diagnosis* / Q000276:immunology*
chemical_list: D015415:Biomarkers; D015796:HLA-B27 Antigen
keywords: HLA B27; ankylosing spondylitis; axial spondyloarthritis; inflammatory back pain; primary care