Observations on severity and activity indices in a therapeutic trial of active Crohn's disease

We describe the use of activity indices during a prospective trial of 91 patients with active Crohn's disease. Data were recorded by experienced physician investigators in four centres, and several activity indices were compared. The indices studied included modifications of the Crohn's Disease Activity Index (CDAI), the Dutch Activity Index, and the European Severity/Activity Index. Correlation was made between each index, between the indices and physician's opinion, and between each index and patient progress. The correlation between indices was generally somewhat higher than that observed during a similar study in the early 1980s. Our results suggest close correlation between the variants of the CDAI, but less good correlation with the Dutch or European indices. There was also good correlation between CDAI variants and physicians' opinion, both as measured on linear analogue scale and as measured by physician action. All assessed indices correlated poorly, however, with short-term patient prognosis. New indices, or combinations of existing datasets, will be necessary to solve this problem.