 As Crohn's disease is a disease with a variety of symptoms that affect quality of life, the quantification of symptoms may be of secondary importance to a quantitative assessment of the effect on quality of life.This has been addressed by the Inflammatory Bowel Disease Questionnaire (IBDQ) and other indices of quality of life for patients with Crohn's disease.The CDAI was developed by WR Best and colleagues from the Midwest Regional Health Center in Illinois, in 1976.