Common outcome measurement tools used in clinical trials include the Crohn’s Disease Activity Index (CDAI) and the Inflammatory Bowel Disease Questionnaire (IBDQ). CDAI helps to quantify improvement or worsening of disease activity. IBDQ is used to assess changes in health-related quality of life (1, 2).

Common Indices Used in Crohn's Disease Clinical Trials

Crohn's Disease Activity Index (CDAI)

The CDAI is the standard for assessment of clinical response to treatment of Crohn’s disease (2). The composite index of overall disease activity was developed by prospectively collecting data for 18 clinical and laboratory values identified by expert opinion (1). Using stepwise multiple regression analysis, eight final items were selected as best predictors of disease activity (Table 1). The total score ranges from 0 to over 600 and is based on patient diary of symptoms over 1 to 7 days and other objective measurements (1, 2). Scores of less than 150 indicate "clinical remission". Mild disease is represented by scores between 151 and 220 and moderate disease is indicated by scores between 221 and 400. Scores over 400 represent severe disease, and scores over 450 represent very severe disease (3). A change in score of 70 to 100 points indicates either improvement or worsening (1, 2).

Table 1: Crohn's Disease Activity Index (from a 1-week diary) (1, 3)

	Item (day)	Weight
1)	No. of liquid or very soft stools	2
2)	Abdominal pain (0-3)	5
3)	General well-being (1-4)	7
4)	Extraintestinal (1 per finding)	20
	Arthritis/arthralgia
	Mucocutaneous lesions
	Iritis/uveitis
	Anal disease (fissure, fistula, etc.)
	External fistula
	Fever > 36.8° C (98.2°F)
5)	Antidiarrheal use	30
6)	Abdominal mass (none-0; equivocal-2; definite-5)	10
7)	47- Hematocrit (males)	6
	42- Hematocrit (females)
8)	100 x (1-body weight/standard weight)	1

Note: Total score range = 0 to 750; higher score = more severe disease; > 150= active disease; 151-220 mild, 221 to 400 moderate, > 400 severe

Clinical Remission

According to the American College of Gastroenterology practice guidelines, clinical remission refers to patients who are asymptomatic or without inflammatory sequelae and includes patients who have responded to acute medical intervention or have undergone surgical resection without gross evidence of residual disease (4). CDAI scores of less than 150 have been graded to indicate "clinical remission" (1, 2).

Clinical Response

When using CDAI scores as an outcome measurement, a clinical response is often defined as a reduction of 70 to 100 points in the CDAI score (1, 2).

Inflammatory Bowel Disease Questionnaire (IBDQ)

Health-related quality of life assessments have become important outcome measurement tools that complement clinical measurements of disease severity (1). The IBDQ is the most extensively used validated disease-specific questionnaire used in IBD clinical trials. The questionnaire includes four categories: Bowel, Emotional, Social, and Systemic. Each of its 32-items scored on a 7-point Likert scale from 1=poorest to 7=optimum function (range 32-224) with a higher score indicating better health-related quality of life (1).

References

1. Irvine EJ. Assessing outcomes in clinical trials. In Satsangi J, Sutherland LR, eds. Inflammatory Bowel Diseases. London: Churchill Livingstone. Elsevier Limited, 2003: 319-333.
2. Sands BE, Abreu MT, Ferry GD, et al. Design issues and outcomes in IBD clinical trials. Inflamm Bowel Dis 2005;11:S22-S28.
3. Best WR, Becktel JM, Singleton JW, Kern F Jr. Development of a Crohn's disease activity index. National Cooperative Crohn's disease study. Gastroenterology 1976;70:439-444.
4. Hanauer SB, Meyers S. Management of Crohn's disease in adults. Am J Gastroenterology 1997;92:559-566.