Lymphedema Quality of Life Inventory (LyQLI)-Development and investigation of validity and reliability

The purpose of this study was to reduce the 188-item Swedish Lymphedema Quality of Life Inventory (SLQOLI) to an abbreviated, clinically useful version (phase 1) and to test it for reliability and validity (phase 2). In phase 1 correlation analysis, factor analysis, content validity assessment and expert panels were used to reduce the number of items in SLQOLI to 45 items, which was named, Lymphedema Quality of Life Inventory (LyQLI). In phase 2, LyQLI was sent to 200 patients with lymphedema. 126 patients completed the questionnaire twice to determine stability of the instrument over time. SF-36 was sent to the patients once, correlations between the three domains in LyQLI and the two sum scores Physical Health (PCS) and Mental Health (MCS) in SF-36 were used to assess concurrent validity. The 188-item SLQOLI was reduced to 45-item LyQLI. Four domains were reduced to three: physical, psychosocial and practical. Reliability estimates using ICC for the physical and psychosocial domains were 0.88 (p < 0.01) and 0.87 (p < 0.01), for the practical domain 0.87 (p < 0.01). Cronbach's alpha coefficients for the three domains were 0.88, 0.92 and 0.88, respectively. The physical domain correlated highly significantly with PCS, psychosocial highly significantly with MCS and practical equally highly significantly to both PCS and MCS. Using skewness coefficients, small floor effects in the items were found. The shorter LyQLI demonstrated good reliability and validity with potential use to assess quality of life in clinic settings and in further cross-sectional studies of patients with lymphedema.