Objectives: To assess the validity (face validity and criterion-related validity) and reliability (test-retest reliability and internal consistency) of a Cantonese (the Chinese dialect predominantly used in Guangdong Province) version of the Cardiff Acne Disability Index.
Design: Questionnaire study.
Setting: Two secondary schools in Hong Kong.
Participants: The Chinese Cardiff Acne Disability Index was translated according to international guidelines including forward-backward translation, reconciliation, and cognitive debriefing. A questionnaire, which was composed of the resultant Chinese Cardiff Acne Disability Index and the Cantonese Dermatology Life Quality Index (for those aged more than 16 years) or the Cantonese Children's Dermatology Life Quality Index (for those aged 16 years or less) was administered to 85 eligible secondary school students.
Main outcome measures: Establishing face validity, criterion-related validity, internal consistency, and test-retest reliability by standard testing.
Results: The face validity was satisfactory. The strength of the relationship between the Chinese Cardiff Acne Disability Index and Dermatology Life Quality Index was large (gammas=0.58) and significant (P=0.004). The strength of relationship between the Chinese Cardiff Acne Disability Index and Cantonese Dermatology Life Quality Index was also large (gammas=0.72) and significant (P<0.001). Regarding internal consistency, Cronbach's alpha was 0.763. Thirty-three students completed the test-retest reliability test, and the resulting correlation of the first and second administration of the Chinese Cardiff Acne Disability Index was strong (gammas=0.795, P<0.001). The intra-class correlation coefficient was satisfactory (0.784, P<0.001).
Conclusion: The Chinese Cardiff Acne Disability Index was equivalent to the original English version, and constitutes a valid and reliable tool for day-to-day clinical use.