Table 1 Methodological steps for a questionnaire validation in two languages

 administering the original list of questions to a limited, unselected sample of subjects;

 identification of mistakes;

 administering the revised list of questions;

 check of each question’s validity (precision) and reliability (reproducibility);

 initial translation from the research language to the foreign language by a bilingual translator;

 back-translation: a new translation, from the foreign language to the research language by a different translator;

 comparison between the two translated versions of the questionnaire;

 proceed in order to obtain two corresponding versions, equally understandable, and a comprehension rate >90 % for each question.