Evaluation of the Turkish version of the Dougados functional index in ankylosing spondylitis

To investigate the reliability and validity of the Turkish version of the Dougados functional index (DFI) in patients with ankylosing spondylitis (AS). The Turkish version of DFI was obtained after a translation and back-translation process. Seventy consecutive patients with AS were enrolled. Patients were requested to complete the questionnaire on the day of admission (first visit), a second time within 24 h after admission (second visit), and on a third occasion. Reliability, validity and reproducibility of the Turkish version of the index were assessed. All the items showed significant correlations with the total index score with r-values ranging from 0.516 to 0.817. Cronbach α score was calculated as 0.908. Significant correlations were found between the total DFI score and Schober test (r=−0.293, P<0.05), occiput-wall distance (r=0.384; P<0.01) finger-to-floor distance (r=0.450, P<0.001), chest expansion (r=−0.331, P<0.01) and Dougados articular index (r=0.352, P<0.05). Good correlations were found between individual DFI items and the total score (r=between 0.533 and 0.882, p< 0.001) for the first and second visits, showing good reproducibility of the index. Conclusion: the Turkish version of DFI has good reliability, validity and reproducibility, confirming its utility for trials in Turkish AS patients.