Defining Moderate Disease Activity and Severity in Crohn's Disease and Ulcerative Colitis

This research aimed to review the literature for definitions of moderate Crohn's disease (CD) and ulcerative colitis (UC).

Real-world evidence suggests that biologics may achieve better outcomes in patients with moderate disease than with severe disease; however, research has been hindered by the lack of consensus on the definition of moderate disease.

We conducted a systematic literature review (SLR) of observational and interventional studies published from 2015 onwards, followed by a targeted literature review (TLR) of phase 3 trials of pharmacological therapies from 2000 onwards, to identify definitions of disease severity. A consensus meeting was convened for experts to discuss how to distinguish moderate from mild or severe disease in clinical practice.

The SLR and TLR included 140 and 101 publications, respectively. Six definitions of moderate CD were identified from 7 publications and 16 definitions of moderate UC from 23 publications. Most definitions were based on Crohn's Disease Activity Index (CDAI) or Mayo score (for UC). Three publications defined moderate CD as CDAI of 200 to 450, 220 to 450, or ≤330. Moderate UC was mostly defined as a Mayo score of 6 to 10 but there was overlap with the range used for severe UC. No definition of moderate disease encompassed quality of life or disease course and prognosis, which were considered important by experts in assessments of disease severity in clinical practice.

A comprehensive and clinically relevant definition of moderate disease is needed to identify patients with CD or UC who can benefit from biologics.