CDAI Calculator

What Is the Crohn's Disease Activity Index (CDAI)?

The Crohn's Disease Activity Index (CDAI) is a standardized scoring system used by gastroenterologists to quantify the severity of Crohn's disease symptoms. It provides a numerical value that helps clinicians assess disease activity, guide treatment decisions, and monitor response to therapy over time.

This calculator implements the original CDAI scoring method, which evaluates eight clinical variables over a seven-day patient diary period. The resulting score helps categorize disease activity into remission, mild, moderate, or severe categories.

How the CDAI Score Is Calculated

The CDAI score is derived from eight weighted components. Each component is multiplied by a specific factor to produce the final score. The components include:

• Liquid or very soft stools — Total number over seven days, multiplied by 2
• Abdominal pain — Sum of daily pain ratings (0 = none, 1 = mild, 2 = moderate, 3 = severe) over seven days, multiplied by 5
• General well-being — Sum of daily well-being ratings (0 = generally well, 1 = slightly under par, 2 = poor, 3 = very poor, 4 = terrible) over seven days, multiplied by 7
• Extraintestinal manifestations — Number of specified complications present (each adds 20 points)
• Antidiarrheal use — Use of opiates or lomotil for diarrhea (adds 30 points if used)
• Abdominal mass — Presence of an abdominal mass (0 = none, 2 = questionable, 5 = definite)
• Hematocrit — Adjustment based on sex and deviation from normal (47 minus hematocrit for men, 42 minus hematocrit for women, multiplied by 6)
• Body weight — Percentage deviation from standard body weight (100 minus percentage of standard weight)

The total score ranges from 0 to approximately 600. Higher scores indicate more active disease.

Interpreting CDAI Results

The CDAI score is typically interpreted using the following thresholds:

• Below 150 — Clinical remission
• 150 to 219 — Mild disease activity
• 220 to 450 — Moderate disease activity
• Above 450 — Severe disease activity

A decrease of 70 to 100 points from baseline is often considered a clinically meaningful response to treatment in clinical trials.

Important Limitations of the CDAI

While the CDAI is widely used in clinical research, it has several limitations that should be considered:

• Subjective components — Pain and well-being ratings rely on patient self-reporting, which can vary between individuals
• Fistulizing disease — The CDAI does not adequately capture disease activity in patients with fistulizing Crohn's disease
• Stool frequency — Patients with prior bowel resections may have higher baseline stool counts unrelated to active inflammation
• Not a diagnostic tool — The CDAI should not be used alone to diagnose Crohn's disease or replace endoscopic evaluation
• Research vs. clinical use — The CDAI is primarily validated for clinical trials; many clinicians prefer simpler indices like the Harvey-Bradshaw Index for routine practice

Practical Use Cases

The CDAI calculator is most commonly used in the following scenarios:

• Clinical trial enrollment — Many studies require a minimum CDAI score (typically 220 to 450) for inclusion
• Treatment response monitoring — Tracking score changes over time to evaluate whether a therapy is effective
• Disease severity documentation — Providing objective documentation for insurance or disability claims
• Patient education — Helping patients understand how their symptoms translate into a measurable disease activity level