Validation of the Swedish Lymphedema Functioning, Disability, and Health (Lymph-ICF-UL) Questionnaire: A cross-cultural psychometric study

BACKGROUND: The Lymphedema Functioning, Disability, and Health Upper Limb (Lymph-ICF-UL) questionnaire is an internationally recognized instrument for assessing patient-reported functional and activity limitations associated with arm lymphedema following breast cancer surgery. This study aimed to validate the Swedish version of the Lymph-ICF-UL and, additionally, to examine its applicability in an extended cohort without diagnosed arm lymphedema but with potential arm-related impairments following axillary surgery for breast cancer. METHODS: A cross-cultural psychometric validation was conducted among 27 Swedish-speaking women aged 44-86 years who had undergone node-positive breast cancer surgery 1 year earlier. Data were collected between October 2024 and March 2025. The questionnaire was back-translated into English, revised, and tested for reliability using a test-retest methodology and assessment of internal consistency. Validity was assessed through construct, face, and content validity. RESULTS: Back-translation required minor grammatical adjustments. Test-retest analysis demonstrated good reproducibility, with intraclass correlation coefficients exceeding 0.80 across all domains. Internal consistency was satisfactory, with Cronbach's alpha ranging from 0.76 to 0.96. Construct validity was moderate, with 70.0% of predefined hypotheses for convergent and divergent validity confirmed. Face and content validity analyses led to clarification of the questionnaire instructions. Overall, the items were considered relevant and adequately comprehensive for assessing perceived impairments. CONCLUSIONS: The Swedish version of the Lymph-ICF-UL questionnaire is a reliable and valid instrument for assessing arm impairment following axillary surgery for node-positive breast cancer, including among individuals without confirmed arm lymphedema.