" Is this questionnaire reliable and valid ? "

Response from MAPI Research Trust:

This question is actually incomplete. The right question should be "has the questionnaire been validated for the population and in the disease area of my study".

A generic questionnaire may have been validated in a men healthy population whereas you wish to use it on a women depressive population. Equally, a gastroenterology-generic instrument may have been validated for use in GERD but not in gastroparesis.

Only a literature review and questionnaire analysis may help identifying the best instrument for use in YOUR study.