Is the validity of cost utility analysis improved when utility is measured by an instrument with ‘home-country’ weights? evidence from six western countries

To test the ‘home-country weights hypothesis’: that the validity of cost utility analyses is improved if utility is measured using an instrument with utility weights obtained from people living in the ‘home-country’—the same country as the patients who are to receive the service which is being evaluated. The convergent validity of multi attribute utility instruments (MAUI) with and without home-country weights was compared. Comparisons were made within and between countries. The analyses employed data from 7933 individuals in 6 Western countries, each of whom completed the questionnaires of 5 MAUI; the EQ-5D-5L, SF-6D, HUI 3, 15D and AQoL-8D. Convergent validity was not greater when an MAUI had home-country weights. Differences in national traits between culturally similar countries may be too small or subtle to affect the utility scores estimated from existing MAUI. This implies that the choice of an MAUI for economic evaluation in culturally similar countries should not be based upon the country in which utility weights were estimated but upon a broader consideration of an instrument’s construct validity.