title: Normative values for the Bath Ankylosing Spondylitis Functional Index in the general population compared with ankylosing spondylitis patients in Morocco.
abstract: BACKGROUND
  The Bath Ankylosing Spondylitis Functional Index (BASFI) has been commonly used in rheumatology to quantify functional disability in patients with ankylosing spondylitis (AS). Our aim was to evaluate the discriminating power of BASFI and determine the best cutoff score of this index in the general population compared with AS patients.
  
  
  METHODS
  A cross-sectional study that included 200 patients suffering from AS and 223 subjects from the general population matched for age and sex was carried-out. The discriminating power of the BASFI by strata of age was evaluated by the area under the Receiver Operating Characteristic curve and the best cutoff was determined by the Youden index.
  
  
  RESULTS
  The mean age of the general population was 39 ± 12 years. 76.7% of them were male. The median BASFI of the healthy subjects and patients was 0.2 and 4.5 (P < 0.001) respectively. The best cutoff of BASFI was 1.5 with a sensitivity of 86% and a specificity of 90%. In the age group of 18-29 years, the best cutoff of the BASFI was 0.9 with a sensitivity of 93% and a specificity of 94%. In the age group of 30-50 years, the best cutoff of the BASFI was 1.5 with a sensitivity of 84% and a specificity of 88%. For those over 50 years of age, the best cutoff of the BASFI was 2.5 with a sensitivity of 84% and a specificity of 97%.
  
  
  CONCLUSIONS
  This study suggests that the discriminating power of BASFI is considered good at any age. The best cutoff of this index increased as age increases as functional disability is associated in part with lifestyle choices and increases with age. The cutoff values of the BASFI that we have presented could be used as a reference benchmark for both clinical practice and research.
authors.affiliation: Rheumatology Department, El Ayachi Hospital, Salé, Ibn Sina University Hospital, Rabat, Morocco. wariaghli@yahoo.com
authors.forename: Ghizlane
authors.initials: G
authors.lastname: Wariaghli
authors.forename: Fadoua
authors.initials: F
authors.lastname: Allali
authors.forename: Kenza
authors.initials: K
authors.lastname: Berrada
authors.forename: Zineb
authors.initials: Z
authors.lastname: Idrissi
authors.forename: Ihsane
authors.initials: I
authors.lastname: Hmamouchi
authors.forename: Redouane
authors.initials: R
authors.lastname: Abouqal
authors.forename: Najia
authors.initials: N
authors.lastname: Hajjaj-Hassouni
mesh_terms: D000328:Adult; D017677:Age Distribution; D015992:Body Mass Index; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D016002:Discriminant Analysis; D004522:Educational Status; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009018:Morocco / Q000453:epidemiology; D009043:Motor Activity; D011237:Predictive Value of Tests; D012372:ROC Curve; D012016:Reference Values; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013167:Spondylitis, Ankylosing / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology