B. Crohn's Disease Activity Index The Crohn 's Disease Activity Index (CD AI), used by the National Cooperative Crohn 's Disease SbJdy (NCCDS) and subsequently by many other multicenter trials, is the most
The American gastroenterologists involved in the preparation of the NCCDS listed the usual clinical symptoms and signs (independent variables) that they considered important indicators of active Crohn 's disease; subsequently, they numerically weighted these independent variables according to the severity and importance of the symptom/sign. The dependent variable with which the independent variables were then compared was the physician's clinical evaluation of severity of disease, subdivided into four categories ranging from "very well" to "very poor." A multiple regression analysis with stepwise deletion was then carried out. thus providing the eight final independent variables that best predicted the physician's overall evaluation (see Table 1).