Initial psychometric evaluation of the Lipedema Quality of Life questionnaire in females with lipedema in Norway

BACKGROUND: There are no validated Norwegian disease-specific patient-reported outcome measures (PROMs) assessing quality of life (QoL) in females with lipedema, limiting evaluation of treatment effect in clinical practice and research. OBJECTIVE: To translate and validate a Norwegian translation of the LIPQOL questionnaire. METHODS: A cross-sectional validation study was performed in 432 females with lipedema in Norway. Descriptive statistics and floor and ceiling effects were assessed. The psychometric properties of the questionnaire were assessed using confirmatory factor analysis (CFA). The overall goodness of fit was evaluated using the root mean square error of approximation (RMSEA), the comparative fit index (CFI) and the Tucker-Lewis index (TLI). Internal consistency was assessed using composite reliability from the CFA. Associations between LIPQOL subscales and RAND-12 physical component score (PCS) and mental component score (MCS) were examined using Spearman correlations. RESULTS: The LIPQOL questionnaire comprises four subscales, Function, Body image, Symptoms, and Feelings. No subscales was affected by floor or ceiling effects. The unmodified CFA shows CFI = 0.929, TLI = 0.922, standardized root mean square residual (SRMR) = 0.073, and RMSEA = 0.079 (90% CI: 0.073 to 0.084). All composite reliability were considered reasonable (ranged from 0.890 to 0.916). Modification indices were evaluated, and two modifications were performed between items 5 and 8, and between items 17 and 18. With modification indices, the overall structure validity showed reasonable, but not unequivocally support for the four factor structure with CFI = 0.944, and TLI = 0.938, SRMR = 0.068, and RMSEA = 0.070 (90% CI: 0.064 to 0.075). Correlation between RAND-12 and LIPQOL subscales were large. Function, Symptoms, and overall quality of life show large correlation with PCS (Spearman's rho = -0.682, Spearman's rho = -0.550, and Spearman's rho = 0.554, respectively) and the subscales feelings and overall quality of life shows large correlation with MCS from RAND-12 (Spearman's rho = -0.685 and 0.608, respectively). CONCLUSION: Initial findings suggest that the Norwegian version of the LIPQOL is a reasonably valid instrument for assessing quality of life in females with lipedema, although the findings do not provide unequivocal support for all aspects of its measurement properties.