The Danish version of Lymphoedema Functioning, Disability and Health Questionnaire (Lymph-ICF) for breast cancer survivors: Translation and cultural adaptation followed by validity and reliability testing

Purpose: To translate and culturally adapt the Lymphoedema Functioning, Disability and Health Questionnaire (Lymph-ICF) for breast cancer survivors with arm lymphedema into Danish and examine its content validity and reliability. Methods: (1) Translation and cultural adaptation was performed in 10 steps following international guidelines (International Society for Pharmacoeconomics and Outcome Research); (2) cognitive interviewing (step 7) was conducted in 15 women with breast cancer related arm lymphedema to explore understandability, interpretation, and cultural relevance; (3) after adjustments, content validity (N = 52) was explored by interviews; and (4) reliability (N = 50) examined by intraclass correlation coefficients (ICC) statistics and Cronbach alpha analysis. Results: Cognitive interviewing lead to an adapted and improved version of the translated questionnaire. Content validity was supported. Internal consistency (alpha) for all questions was .98 and ranged for the different domains between 0.92 and 0.97. Test-retest reliability for the total score was highly satisfactory, ICC = 0.95, standard error of measurement (SEM) = 4.5 and smallest detectable change = 12.5. ICC values for the domains ranged from 0.84 to 0.94. SEM values differed for the domains, 6.4 (physical function), 5.7 (mobility activities), 7.09 (life and social activities), 9.1 (mental functions), and 10.2 (household activities). Conclusion: The translated and adjusted Lymph-ICF DK (Denmark) is reliable and valid, allowing for assessing self-reported impairments in function, activity limitations, and participation restrictions in Danish patients with breast cancer-related arm lymphedema.