EQ-5D versus SF-12 in coronary patients: are they interchangeable?

Objectives: The aim of this study was to compare EuroQol five-dimensional (EQ-5D) utility scores and six-dimensional health state classification (SF-6D) utility scores (derived from the 12-Item Short-Form Health Survey [SF-12]) by using a large European sample of patients with stable coronary heart disease. Special attention was given to country-specific results.

Methods: Data from the EURopean Action on Secondary and Primary Prevention by Intervention to Reduce Events III (EUROASPIRE III) survey were used. Patients hospitalized for a coronary artery bypass graft, percutaneous coronary intervention, acute myocardial infarction, or myocardial ischemia were interviewed and examined at least 6 months after their acute event. Health-related quality of life was assessed by using the EQ-5D and the SF-12. SF-12 outcomes were converted to SF-6D utility values, allowing comparison between both measures.

Results: Both EQ-5D and SF-6D results were available for 7472 patients with coronary heart disease from 20 European countries. The measures were significantly correlated (intraclass correlation coefficient = 0.536); however, large differences between the two measures remain. A total of 28.8% of the patients reported a ceiling effect on the EQ-5D instrument, whereas only 4.2% of the patients reported full health based on the SF-6D. Especially the mental component does not seem to be completely captured by the EQ-5D instrument. Furthermore, patients with worse EQ-5D outcomes were more likely to have better SF-6D results, whereas patients with better EQ-5D outcomes were more likely to have worse SF-6D results.

Conclusions: Both measures are not interchangeable. Whereas the main disadvantage of the EQ-5D questionnaire is its ceiling effect, the potential advantages of SF-12 might disappear when converting the outcomes into an SF-6D utility, because of the small differences between patients.