Do response scales mean the same thing across countries? Cross-cultural comparison of health response scales in the United States, United Kingdom, and Germany

Patient-reported outcome measures often assume that translated response options represent comparable gradations of difficulty, frequency, or severity across countries, yet this is rarely tested directly. This study investigated how general population adults in the United States, United Kingdom, and Germany interpreted EQ-HWB-9 response options across three response scale types: difficulty, frequency, and severity. A cross-sectional online survey was conducted between September 2025 and February 2026 using quota sampling on age and gender in all countries and race/ethnicity in the US (US n = 348, UK n = 312, Germany n = 293). Participants completed a slider positioning task for each of nine EQ-HWB-9 dimensions and a ranking task for each of three response scale types. In the slider task, intermediate response options were positioned on a 0–100 scale anchored by the two extreme options; in the ranking task, randomized response options were ordered. Discrimination between adjacent response levels was assessed using Cohen’s d (small ≤ 0.49, medium 0.50–0.79, large ≥ 0.80). Cross-country differences in slider means were tested using one-way ANOVA. Ordinal structure was preserved across all three countries: slider means increased monotonically across response levels in every domain, and the majority of respondents in each country correctly ordered the five response levels (73–77% frequency, 73–80% difficulty, 77–82% severity), with a small additional group producing a full reversal; severity labels were ordered most accurately and frequency least. Discrimination between adjacent levels, however, differed. The US and UK showed large, consistent spacing (mean d = 0.98 and 1.07), whereas Germany discriminated somewhat less (mean d = 0.84, still large), particularly on the difficulty scale. In an exploratory analysis, disordered ordering was associated with limited health literacy and lower education and not with demographic or health characteristics. Preserved ordering should not be mistaken for quantitative equivalence. Response option testing may identify cross-national differences in interpretation that are not detected through standard translation and development procedures and may help strengthen cross-country comparability.