Development and psychometric testing of Korean language versions of 4 neck pain and disability questionnaires.
Cohort study. To develop and establish the psychometric properties of Korean versions of 4 neck pain and disability questionnaires: the Neck Disability Index, Neck Pain and Disability Scale, Functional Rating Index, and Short Form McGill Pain Questionnaire (SFMPQ). To our knowledge, there are no published Korean language neck pain and disability measures. Versions of each questionnaire in idiomatic modern Korean were developed with a process involving initial independent translation, synthesis of the translations, independent back translation, and review by an expert committee to achieve equivalence with the original English. Psychometric testing of the questionnaires with 261 subjects was undertaken to examine test-retest reliability, internal consistency, discriminative validity, and longitudinal construct validity. Test-retest reliability of the translated versions of the 3 disability questionnaires was excellent (intraclass correlation coefficient[2,1] = 0.86-0.90). High internal consistency was found in the 3 disability questionnaires (Cronbach-alpha ranged from alpha = 0.88 for the Functional Rating Index to alpha = 0.96 for the Neck Pain and Disability Scale, and 0.82 for the SFMPQ). The visual analog scale subscale of the SFMPQ was the most responsive of the subscales (effect size = 1.44, standardized response mean = 1.37). The visual analog scale was also the most responsive pain and disability index in internal responsiveness analysis, although disability indexes showed marginally better responsiveness when compared with external standards. No floor or ceiling effects were observed. We conclude that the questionnaires were successfully translated and show acceptable measurement properties, and, as such, are suitable for use in clinical and research applications.