Recent decades have seen increasing use of questionnaires by both clinical dermatologists and researchers. These easy-to-use instruments are valuable aids to economically and systematically collecting large amounts of data for analysis.1 Questionnaires have the advantage over interviews because they eliminate bias arising from an interviewer's influence. Another advantage is that they provide quantitative data to facilitate comparisons and generalizations. Before a tool can be used, however, its measurement properties must be demonstrated by means of a study of the questionnaire's validity, reliability, and responsiveness to change.2

Validation demonstrates that a tool measures what it claims to measure, thereby showing that it is fit for the purpose the developers intended. The validation process is dynamic and ongoing, and a tool with more robust psychometric properties has internal consistency, providing the basis for using it in different cultures, populations, and subjects.2 Before a tool that was developed and validated in one language can be recommended for use in another language, however, it must undergo a translation process that includes cultural as well as language adaptation. This process of validated translation and adaptation to different communities is indispensable for producing a standardized measurement tool that can be used in multicenter studies across borders.

The cultural adaption of the Early Arthritis for Psoriatic Patients questionnaire, as reported in this issue,3 is therefore a step toward providing us with a valuable tool for studying patients with psoriasis in Spain.