Validation of a Chinese version of the Jaw Functional Limitation Scale in relation to the diagnostic subgroup of temporomandibular disorders

BACKGROUND: Oro-facial function is usually impaired by temporomandibular disorders (TMDs). Several studies on TMDs have used the Jaw Functional Limitation Scale (JFLS) to assess mandibular dysfunction. However, it was originally created in English and hence needs to be validated for use among Chinese people. OBJECTIVE: To develop a Chinese version of the JFLS for Chinese TMD patients and to investigate the validity and reliability of the scale. METHODS: Content validity and temporal stability were evaluated at two different occasions. The reliability and validity of the JFLS were tested in 483 TMD patients. Cronbach's alpha coefficient and split-half reliability were used to assess internal consistency, while the validity was evaluated by factor analysis. RESULTS: Three factors were extracted during exploratory factor analysis, accounting for 62.39% of the variance. The three-factor model was then measured using confirmatory factor analysis (chi(2) /df = 3.6, root mean square error of approximation = 0.091, comparative fit index = 0.896). Internal (coefficient alpha values of .906 for all items and Guttman split-half reliability of 0.756) and test-retest (intra-class correlation coefficient = .851-.897, 95% confidence interval = 0.656-0.950) reliabilities were excellent. CONCLUSION: The Chinese version of the JFLS is reliable and valid for use in Chinese TMD patients.