Psychometric evaluation of the Persian version of the Lymphedema Life Impact Scale (LLIS, version 1) in breast cancer patients

Abstract

Background: Despite the high prevalence of lymphedema in Iranian breast cancer patients, there is no valid instrument for measuring quality of life in this population. The aim of this study was to assess reliability and validity of the Persian version of Lymphedema Life Impact Scale (LLIS) in breast cancer patients. Methods: Forward-backward procedure was applied to translate The LLIS from English into Persian. The LLIS is an 18-item measure of physical, psychosocial, and functional impairments caused by lymphedema. Experts and patients assessed content and face validity, respectively. Discriminant validity was evaluated by comparing breast cancer patients with and without lymphedema. Convergent validity was assessed by comparing LLIS score with SF-36 (functional component) and the EORTC-QLQ-C30 (functional component). The construct validity also was evaluated using confirmatory and exploratory factor analyses. Internal consistency was evaluated by Cronbach's alpha coefficient. Stability was assessed by test-retest analysis over a one-week interval in 13 patients. Results: In all 446 breast cancer patients were entered into the study. The content and face validity of Persian version of LLIS were acceptable and minor corrections were applied in final version. The questionnaire differentiated well in patients' with and without lymphedema and not lending support to its discriminant validity. Confirmatory factor analysis showed a good fit for the data. Cronbach's alpha coefficient in physical, psychosocial and functional subscales were 0.873, 0.854 and 0.884 respectively. Intra-class correlation coefficient of total score of the LLIS was 0.96. Conclusions: The findings of this study suggest a first indication that reliability and validity of the Persian version of LLIS in patients with breast cancer induced lymphedema was good. Application of this instrument for identifying problems of patients with upper extremity lymphedema may be helpful in designing interventions to improve quality of life.