Why are quality of life instruments not recognized as reference measures in therapeutic trials of chronic skin disorders?

Patient-reported outcomes, especially heath-related quality of life (HRQOL) outcomes, are particularly relevant for chronic skin disorders (CSDs), because lesion scores such as PASI are less meaningful in making therapeutic decisions. Patient perception of the disease impact, such as HRQOL, should be the main outcome measure in therapeutic trials for CSDs, especially for expensive biotherapies. To be credible as reference measures, dermatology-specific instruments of HRQOL must generate similar scores in different countries and different cultures. Because none of the currently used instruments--e.g., the Dermatology Life Questionnaire Index (DLQI) and Skindex--fulfills this requirement, it is important to generate new instruments or adapt existing ones.