Crohn's Disease Activity Index (CDAI) has been developed to assess whether or not the pathology is progressing.
The index is the sum of 8 components, (P1-P8) to each of which is assigned a specific weight (1). The following table indicates, for each parameter, the input values with their respective scores.
The value of each parameter is multiplied by a 'Weight' factor, shown in the right column of the table.

Parameter Input and score Weight
P1. Number of liquid or soft stools
(evaluated within a week)
blank field
(integer, maximum two digits)
P2. Daily abdominal pain
(evaluated within a week)
0 = none
1 = mild
2 = moderate
3 = severe
P3. Patient well-being
(evaluated within a week)
0 = very well
1 = slightly below par
2 = poor
3 = very poor
4 = terrible
P4. Complications No (0 points)
Yes (drop-down menu with multiple selection; each selected complication is counted with 1 point)
  • arthralgia or arthritis
  • iritis or uveitis
  • erythema nodosum, pyoderma gangrenosum or aphthous ulcer
  • fissures, anal abscesses or fistulas
  • other fistulas
  • fever during the previous week
P5. Use of diphenoxylate or opiates as anti-diarrheal No = 0
Yes = 1
P6. Abdominal mass 0 = none
0,4 = dubious
1 = present
P7. Hematocrit a. selection Male/Female
(standard values: 47 for males and 42 for females)
b. insert current % value (integer, maximum two digits)

the calculator shows the difference (standard-current), expressed as number of percentage points
P8. Body weight a. Height (cm) – integer, 3 digits
After the insertion of height value, the calculator displays standard weight in kilograms, according to Keys formula:
Standard weight for men = (height in m)2 x 22.1
Standard weight for women = (height in m)2 x 20.8

b. Current weight (integer, maximum three digits)

The calculator shows the % change vs. the standard weight.
Calculation formula: = 100 x ((Standard-Current)/Standard)

In case of excessive negative change, the computer returns for this parameter a maximum score of -10 points

Calculation formula: CDAI = (P1 x 2) + (P2 x 5) + (P3 x 7) + (P4 x 20) + (P5 x 30) + (P6 x 10) + (P7 x 6) + P8

In the formula, the last parameter (P8) is not multiplied by the relevant 'weight factor', given that in this parameter the 'weight factor' is equal to 1.

The most appropriate use of CDAI is to perform periodic evaluations, verifying the score over time. In clinical trials in Crohn's disease using CDAI, clinical response is defined as a decrease in score of at least 70 points and at least 25% in subjects with baseline CDAI score greater than or equal to 220 (2). The generally accepted decoding criterion is as follows:

Score Decoding
≤ 150 remission
151-219 mild activity
220-450 moderate activity
> 450 severe or very severe activity
  • 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 (3): 439–444.
  • Sands B, Anderson F, Bernstein C, Chey W, Feagan B, Fedorak R, Kamm M, Korzenik J, Lashner B, Onken J, Rachmilewitz D, Rutgeerts P, Wild G, Wolf D, Marsters P, Travers S, Blank M, van Deventer S. Infliximab maintenance therapy for fistulizing Crohn's disease. N Engl J Med 2004; 350 (9): 876–885.
  • Sostegni R, Daperno M, Scaglione N, et al. Review article: Crohn’s disease: monitoring disease activity. Aliment Pharmacol Ther 2003; 17: 11-17.