Multi-country quantitative examination of visual analogue scale versions with the EQ-HWB-9

Visual analogue scales (VAS) yield interval-level data that may complement an instrument’s descriptive system. While existing EQ-5D instruments include the EQ VAS, the experimental EQ-HWB-9 currently lacks an accompanying VAS. Prior mixed-methods evidence in a small US sample ( n = 34) suggested that candidate VAS constructs were perceived differently qualitatively yet did not differ meaningfully in quantitative ratings. To further inform the inclusion of an appropriate VAS with the EQ-HWB-9, this study aimed to examine the extent to which versions of the VAS reflected the content of the descriptive system across three countries. Adults from the US, UK, and Germany completed an online survey with a modified, experimental EQ-HWB-9 and three VAS versions with 7-day recall periods specified as: (1) Health (2), Health and Wellbeing (HWB), and (3) Quality of Life (QoL), in a random order. Means, effect sizes, correlations, and agreement between ratings were compared across VAS versions. Construct-specific convergent validity was examined by correlations with EQ-HWB-9 items and external anchors. Multiple linear regression models estimated the variance in different VAS ratings explained by EQ-HWB-9 items. Subgroups by country and among caregivers were also analyzed. Among n = 916 ( n = 319 US, n = 312 UK, n = 285 Germany) respondents, mean ratings were 70.9(19.5) for VAS-Health, 68.7(20.2) for VAS-HWB, and 68.7(20.6) for VAS-QoL. While ratings differed significantly by construct, the effect was trivial ( p < 0.01; all Cohen’s d < 0.20), and inter-construct agreement was good (ICC = 0.77). EQ-HWB-9 items explained comparable variance across constructs (adjusted R² = 0.37–0.42), but with construct-specific differential sensitivity: Pain and self-rated health correlated most strongly with VAS-Health, while Sad/Depressed, Lonely, life satisfaction, and relationship satisfaction correlated most strongly with VAS-QoL. VAS-HWB was most explained by a balanced mix of physical and psychosocial items. Country produced negligible improvement in R 2 when added to models (ΔR² < 0.005). When asked which construct best captured the content of the EQ-HWB-9, 45.9% of respondents selected HWB and 59.9% ranked HWB as the preferred construct, though 39.1% indicated all three constructs equally captured the measure’s content. The three VAS versions yielded similar aggregate ratings and comparable overall explanatory power but differed in terms of which EQ-HWB-9 dimensions predicted their scores. VAS-HWB demonstrated a balanced alignment with the EQ-HWB-9 in terms of coverage of items predicting ratings, supporting it as a candidate for further investigation with the EQ-HWB-9.