title: A Dutch version of the functional index for ankylosing spondylitis: development and validation in a long-term study.
abstract: A Dutch Functional Index (DFI) for AS has been developed, containing 37 questions in essence this is a modification of a French index with additional questions. Internal consistency, reproducibility, criterion and construct validity and sensitivity to change were studied in different groups of AS patients. In a group of 149 patients the questionnaire was completed and internal consistency calculated (Cronbach's alpha = 0.94) after exclusion of three items. Reproducibility was studied in 39 patients with stable disease; Pearson correlation was 0.94. Criterion validity, against a 'gold standard' i.e. experts' observation of 25 items, was studied in 19 patients; r = 0.85. In a 48-week NSAID study patients were enrolled after a washout period: DFI scores before and after treatment showed significant improvement (P < 0.02). There were 187 DFI with corresponding clinical measurements, correlations varied from -0.30 to 0.68. Estimated measurement-remeasurement correlation was 0.87. The DFI is, thus, a potentially useful instrument, which is valid, reliable and sensitive to the effects of NSAID treatment.
authors.affiliation: Department of Rheumatology, University Hospital Nijmegen, St Radboud, The Netherlands.
authors.forename: M C
authors.initials: MC
authors.lastname: Creemers
authors.forename: M A
authors.initials: MA
authors.lastname: Van 't Hof
authors.forename: M J
authors.initials: MJ
authors.lastname: Franssen
authors.forename: L B
authors.initials: LB
authors.lastname: Van de Putte
authors.forename: F W
authors.initials: FW
authors.lastname: Gribnau
authors.forename: P L
authors.initials: PL
authors.lastname: Van Riel
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D013167:Spondylitis, Ankylosing / Q000503:physiopathology*; D011795:Surveys and Questionnaires / Q000592:standards*; D013997:Time Factors