Translation and construct validity of the Lequesne index for Arab speaking North African patients with osteoarthritis of the knee]

OBJECTIVE: To translate in Arabic and validate the Lequesne index for use in Tunisian. BACKGROUND: No instrument wording in Arabic language and validated in an Arab population to measure lower limb functional disability caused by OA. DESIGN: Arab translation was obtained using the "forward translation/backward translation" method. Adaptations were made after a pilot study. Patients with symptomatic knee osteoarthritis fulfilling the revised criteria of the American College of Rheumatology were included. Impairment outcome measures (VAS pain; knee mobility; Kellgren's radiological score); disability (the maximum distance walked; WOMAC index) and Beck depression scale were recorded. Inter rater reliability was assessed using the intra-class correlation coefficient (ICC) and the Bland and Altman method. Construct validity was investigated using the Spearman rank correlation coefficient (convergent and divergent validities) and a factor analysis was performed. Internal consistency of each factor was assessed by Crohnbach alpha coefficient. RESULTS: One hundred and three patients were included. All questions were acceptable and retained. Inter rater reliability was excellent with ICC = 0.91. The Bland and Altman method showed distribution of differences homogenous and no systematic trend. Expected divergent validity and convergent validity were observed, suggested good construct validity. Two main factors were extracted by factor analysis of the Lequesne, and explained more than 55% of the cumulative variance, the first factor represents disability and the second represents pain and stiffness. Crohnbach alpha coefficient was, respectively, 0.68 for factor 1 and 0.54 for factor 2. In conclusion, we translated and adapted the Lequesne index into Arabic to suit Tunisian people. Translated questionnaire is reliable and valid. Although the scale was validated in a Tunisian population, we expect that it can suit other Arab populations especially North Africans. Further studies are needed to confirm such hypothesis.