NEW research is exposing a major blind spot in inflammatory bowel disease (IBD) care: there is still no clear, consistent definition of what “moderate” disease actually means.
The study reviewed how moderate disease is defined in both Crohn’s disease and ulcerative colitis, uncovering significant variation across clinical trials and real-world studies, an issue that could be holding back optimal treatment strategies.
Wide Variation in Definitions
Researchers analysed over 240 publications, including observational studies and Phase III clinical trials. The findings showed that definitions of moderate disease vary widely, with six different definitions identified for Crohn’s disease and 16 for ulcerative colitis.
Most rely heavily on scoring systems such as the Crohn’s Disease Activity Index (CDAI) or the Mayo score. However, even within these tools, thresholds differ. For example, moderate Crohn’s disease has been defined using CDAI ranges from 200 up to 450, while moderate ulcerative colitis is often defined as a Mayo score of 6 to 10—overlapping with criteria sometimes used for severe disease.
Missing the Bigger Picture
Perhaps more importantly, current definitions fail to capture what clinicians actually consider meaningful. None of the identified definitions incorporated factors such as quality of life, long-term disease trajectory, or prognosis.
Experts involved in the study emphasised that these elements are critical in real-world decision-making, suggesting that existing frameworks may be too narrow and overly reliant on numerical thresholds.
Impact on Treatment Decisions
This lack of clarity has real consequences. Emerging evidence suggests that patients with moderate disease may respond particularly well to biologic therapies—sometimes even more so than those with severe disease.
However, without a clear and consistent definition, identifying the right patients for early intervention becomes challenging, potentially delaying access to more effective treatments.
Need for a Practical, Unified Approach
The authors argue that a more comprehensive and clinically relevant definition of moderate disease is urgently needed. Such a definition would need to go beyond traditional scoring systems and reflect the broader patient experience, including symptom burden and disease progression.
Moving Toward Precision Care
As IBD management continues to shift toward earlier and more targeted intervention, defining disease severity accurately becomes increasingly important.
Right now, “moderate” IBD sits in a grey zone. Until that is fixed, clinicians are left making high-stakes treatment decisions without a clear framework, something this study makes hard to ignore.
Reference
Chou C et al. Defining Moderate Disease Activity and Severity in Crohn’s Disease and Ulcerative Colitis. Journal of Clinical Gastroenterology. 2026;DOI: 10.1097/MCG.0000000000002349
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