Adaptation and validation of an Arabic version of a 10-item patient-reported outcome measure of physical function in rheumatoid arthritis

Aim To adapt and validate an Arabic version of the short form of physical function measure (PF-10a), a generic questionnaire for physical function, in Egyptian patients with rheumatoid arthritis (RA). Methods After standardized linguistic validation of the Arabic version of PF-10a, with forward and backward translation, the questionnaire was completed by 70 Egyptian RA patients who were diagnosed according to American College of Rheumatology/European League Against Rheumatism 2010 classification criteria, on two occasions 3-5 days apart. The internal consistency and test-retest reliability were evaluated using Cronbach's alpha and intra-class correlation. The content validity of the Arabic PF-10a was tested against Health Assessment Questionnaire Disability Index (HAQ-DI), Clinical Disease Activity Index (CDAI) and Disease Activity Score in 28 joints using erythrocyte sedimentation rate (DAS28-ESR). In addition, serology results, hand radiographs, and treatments received were all recorded. Results Most of our patients were female (88.6%) with a mean age of 49.2 +/- 10.5 years. They had a mean disease duration of 7.3 +/- 7 years and an active disease with a mean CDAI of 33.1 +/- 12.6. The mean value of PF-10a was 34.6 +/- 6.2. The Cronbach's alpha for Arabic PF-10a was 0.904. Intra-CLASS CORRELATION was 0.897. Arabic PF-10a correlated strongly with HAQ-DI (-0.746), moderately with CDAI, patient global assessment, and pain (-0.457, -0.417, and -0.371 respectively). Conclusion The validation study showed that the Arabic PF-10a had acceptable psychometric characteristics, in terms of internal consistency and construct validity. The Arabic PF-10a is a reliable and valid instrument to be used by Arabic RA patients.