Developing and evaluating cross-cultural instruments from minimum requirements to optimal models.

In the age of increased international collaboration in medical research, the necessity of having at hand cross-culturally applicable instruments for the assessment of health-related quality of life (HRQL) in clinical trials has been voiced. Several important theoretical bases leading to cultural bias in HRQL measurement include differences in definitions of HRQL across national and cultural contexts, levels of observation relied upon to indicate HRQL states, and the significance or weight placed upon the various HRQL states or dimensions measured. Despite a growing literature on the development and evaluation of existing HRQL measures in other cultures, comprehensive sets of procedures or requirements for the international part of development and evaluation are lacking. This paper reviews major approaches to developing international HRQL measures, and discusses various methods and criteria that have been recommended for evaluating measurement equivalence in comparisons of research across national and cultural contexts. A summary of recent trends and advances in international HRQL assessment is presented.