Abstract
Several activity indices have been developed to assess the efficacy of new therapies for inflammatory bowel disease. The ideal index should be simple to administer and quantitative. It should be a composite of subjective symptoms, objective findings and laboratory markers of inflammation. Any newly developed indices should be assessed for validity, reliability and responsiveness before application in clinical trials. Obstacles to standardizing disease activity relate to the heterogeneity of disease manifestations, the characteristics of the study population, the therapy being tested, the investigators' preference for which index to apply and the attributes of the index. Examples of available indices are identified, some of their limitations are discussed, and guidelines for how to select an index for a clinical trial are outlined.