VAS value set still has its own application value compare with TTO value set of EQ-5D-3L in Chinese population

To develop a Chinese visual analogue scale (VAS) value set for Europe Quality of Life Questionnaire (EQ-5D-3L) and compare it with the time trade-off (TTO) value set which was constructed based on the same sample.

An adapted Measurement and Valuation of Health (MVH) protocol was applied with VAS method. EQ-5D-3L was used in face-to-face interviews conducted by trained interviewers with participants selected via multi-stage stratified clustered random sample. Fifteen hypothetical health statuses (11 random states in MVH protocol, plus full health, severe problems for all dimensions, unconscious, and death) were assigned for assessment individually. Ordinary least square (OLS), general least square (GLS), and weighted least square (WLS) models were constructed. Five categories of indices, including quality of original data, distribution of rescaled values, goodness of fit of models, distribution of predicted values, and dimensions order were adopted to compare between Chinese VAS and TTO value sets.

All 5,939 participants aged 15 and over were completely interviewed; 5,884 eligible participants were included in constructing models. Model 2 was the best for having 4 out of 7 indices of goodness of fit. Comparing with the TTO value set, Adjusted R-square of Model2 increased from 0.354 to 0.670;the mean absolute error decreased from 0.0838 to 0.0319; and the Pearson correlation coefficient between predicted and mean values increased from0.8989 to 0.9837. Model 2 gave uniformly lower values than Chinese TTO value set. VAS method had a higher responsive rate, less inconsistency, lower skewed values, and better goodness of fit values.

We recommend VAS value set, Model 2, as the reference of scoring algorithm when using EQ-5D-3L in large scale survey of Chinese population.