Reliability and Validity of Function Score for Adult Tibetans with Kashin Beck Disease in Aba Tibetan Autonomous Area in Sichuan Province

To validate the function score for adult Tibetans with Kashin-Beck disease (FSAT- KBD) measuring daily life and work functional status of KBD patients.From September to October 2010, 352 adult KBD patients in Rangtang County of Aba Tibetan autonomous region were invited to complete FSAT-KBD. The internal consistency of FSAT-KBD was assessed using Cronbach's alpha coefficients. Principal component analysis with varimax rotation was performed to explore factor structure of the instrument, with item-domain correlations being examined using Spearman's rank correlation tests. Discriminant validity of the FSAT-KBD was assessed by comparing scores of the respondents with different ages and different functional status. Convergent validity of the FSAT-KBD was assessed through a comparison with the medical outcomes study short form health survey (SF-12) and visual analogue scale (VAS).338 KBD patients (a response rate of 96.0%) completed the questionnaire in an average of (3.2 +/- 1.6) min. The instrument achieved a Cronbach's alpha of 0.945, with item-to-domain correlations exceeding 0.0. Two latent factors were extracted, which explained 72.8% of the total variance. The factor structure fitted well with our conceptual hypothesis. Respondents with different age, duration of suffering and number of affected joints had different FSAT-KBD scores. The FSAT-KBD results were correlated with those of SF-12 and VAS.FSAT-KBD is a reliable and valid instrument for measuring daily functional status of adult KBD patients in Aba Tibetan autonomous area in China.