Accepted Instruments for Rating and Classifying Inflammatory Bowel Disease
Bryan G. Sauer
Brian Behm
INTRODUCTION
Clinical research in inflammatory bowel disease (IBD) continues to evolve. Typically, trials focus on clinical, endoscopic, or quality-of-life outcomes to determine whether new therapies are more efficacious than the standard of care. A standardized and validated way to compare disease activity in IBD is thus essential. Ideally, a scoring system for IBD would be simple to administer, reproducible, valid (i.e., it measures what it intends to measure), and responsive to change (1). Multiple scoring systems for IBD disease activity have been created (Table 4.1), which often make it difficult to interpret and compare results from different trials. This chapter will focus on the most widely used instruments for both Crohn’s disease (CD) and ulcerative colitis (UC). We will discuss tools for measuring clinical and endoscopic disease activity and review quality-of-life scoring systems.
CROHN’S DISEASE
Instruments to assess disease activity in CD have been designed to measure clinical disease activity, endoscopic activity, and perianal disease activity. Several scoring systems have been developed and validated in the clinical arena, and the most commonly used instruments for each category are discussed here.
Clinical Disease Activity
Crohn’s Disease Activity Index
In 1970, investigators in the National Cooperative Crohn’s Disease Study developed a disease assessment instrument known as the Crohn’s Disease Activity Index (CDAI). Through multiple regression methods, 8 of 18 variables were identified that best predicted disease severity, and a weighted scoring system was developed. The CDAI has both subjective and objective findings as shown in Table 4.2. To better assess some of the subjective variables, a 7-day diary of disease-related symptoms is completed by the study subject before a score is calculated (2).
Because the CDAI has been used extensively in previous trials, it enables comparisons between studies. CDAI scores range from 0 to approximately 600. The definitions of clinical response and clinical remission in the CDAI can vary (Table 4.3), but most clinical trials define a clinical response as a decrease in CDAI of 70 or 100 points, and clinical remission as a CDAI ≤150. In general, a CDAI >220 is classified as moderate disease and a CDAI >450 as severe disease (2, 3 and 4).
The CDAI has been prospectively validated and remains the most widely used scoring system for CD activity today. It is considered the gold standard for measuring clinical disease activity in CD. However, limitations do exist, such as interobserver variability in scoring, the inclusion of subjective variables, such as general well-being and intensity of abdominal pain, and the need for a 7-day diary to complete the CDAI calculation. Furthermore, the CDAI does not accurately assess disease activity in patients with significant fistulizing disease or in patients with an ileostomy or colostomy (3,5).
TABLE 4.1 Measurements of Disease Activity in Crohn’s Disease and Ulcerative Colitis | ||||||||||||||||||||||||||||||||||
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Harvey-Bradshaw Index (Simple Index)
The Harvey-Bradshaw Index was developed in 1980 to simplify the CDAI by eliminating the need for the weeklong symptom diary and weighted measurements required by the CDAI. The index is based on five categories taken from the CDAI, including general well-being, abdominal pain, number of liquid stools per day, presence of an abdominal mass, and complications of CD, such as arthralgias, uveitis, or perianal disease (Table 4.4). There is good correlation between the Harvey-Bradshaw Index and the CDAI (r = 0.93), and it has been prospectively validated (6).
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