Reliability of a Self-Administered Medical Questionnaire

A self-administered patient questionnaire comprising 204 commonly used inventory-by-systems questions was tested for reliability. By testing and retesting each medical question both on forms and on cards, it was shown that inconsistency in responses was not related to the mode of questioning, but to the content of the questions. For the total of 204 questions, 95% of the patients changed their answer to less than 6% of the questions. Patients were much more likely to change their second answer when their first response was a yes, than when a no. An overall score was developed which ranked each question as to its relative reliability.