Crohn’s Disease Activity Index (CDAI)

Evaluates disease severity based on patient symptoms, weight and haematocrit.

Read more about the index parameters, the scoring method and the original study in the text below the calculator.

The Crohn’s Disease Activity Index offers information about disease severity in patient’s suffering from Crohn's disease of the small bowel or colon. General symptoms (abdominal pain, presence of liquid stools etc.), haematocrit and weight factors are considered.

The CDAI was validated as gold standard in assessing disease severity (progress or lack of progress), however, was found to have little to no prognostic value.

The CDAI was developed by Best el al. using data from 112 patients with Crohn's disease of the small bowel, colon, or both.

From 18 parameters collected, 8 were deemed most clinically relevant and were awarded different weights to form a CDAI score.

The score offers information about severity of Crohn’s disease:

CDAI score Crohn’s disease severity
<150 Remission
150 – 220 Mild
221 – 450 Moderate to severe
>450 Severe


Liquid stools

Total no. of liquid/soft stools over the last 7 days

Abdominal pain

Average daily rating of the abdominal pain in the past 7 days using the following scale: 0 = None, 1 = Mild, 2 = Moderate, 3 = Severe.
Abdominal pain over the last 7 days

General well being

Average daily rating of the general well being in the past 7 days using the following scale: 0 = Generally well, 1 = Slightly under par, 2 = Poor, 3 = Very poor, 4 = Terrible.
General well being over the last 7 days

Extra-intestinal complications - select any that apply


Diarrhea treatment

Anti-diarrhea drug use

Abdominal mass

Possibility of presence of an abdominal mass

Haematocrit in %

Hct %


Current body weight
Ideal body weight
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The scoring method explained

This is an assessment based on the patient’s diary of symptoms for the past 7 days concerning stool and general health along with evaluation of clinical symptoms and laboratory results.

The CDAI is most often used in medication studies because it provides a reliable cut off value for Crohn’s disease remission.

The following table discusses the 8 parameters used, along their weight in the total CDAI score:

CDAI item Description Points/ Value Adjustment factor
Liquid stools Cumulative number of liquid or soft stools Sum for last 7 days x2
Abdominal pain
None = 0
Low Intermediate = 1
High Intermediate = 2
Severe = 3
Daily assessment of pain on an ordinal scale Sum of ratings for last 7 days x5
General well being
Well = 0
Low Intermediate = 1
High Intermediate = 2
High = 3
Terrible = 4
Daily assessment of general wellbeing on an ordinal scale
(Criticised for being highly subjective)
Sum of ratings for last 7 days x7
Extra-intestinal complications Arthritis/arthralgia
Skin/mouth lesions
Peri-anal disease
Other fistula
Fever >37.8 °C, >100 °F (in the last week)
1 point for each complication x20
Diarrhea treatment Under treatment with Lomotil, Loperamide or Opiates 1 point if under treatment x30
Abdominal mass
None = 0
Questionable = 2
Definite = 5
Checks whether an abdominal mass is likely present Number of points of selection x10
Haematocrit in % Applies a gender differentiated formula Male = (47 - user value) x6
Female = (42 - user value)
Weight Current body weight 100 x (1 - current weight/standard weight)

Please note that although the Crohn’s disease activity index is accurate in determining the progress or lack of progress, this is not a prognostic tool.

It only refers to disease severity and “generally speaking, CDAI scores below 150 indicate a better prognosis than higher scores”.

The original study proposed a remission cut off value of 150, whilst subsequent studies have adjusted this to 200 or even 250.

This model has been criticised for being too complex (need for patient recollection) and for being subjective in some parts of the assessment.

There are other Crohn’s disease assessment tools like the Harvey Bradshaw Index which is a simplified version of the CDAI.


Score interpretation

The possible scores from the CDAI are between 0 and 600, where the higher the score, the more severe the disease stage.

The following table introduces the four types of disease severity and their associated CDAI scores:

CDAI score Crohn’s disease severity
<150 Remission
150 – 220 Mild
221 – 450 Moderate to severe
>450 Severe

According to the above table, the disease activity cut off point is at 150 whilst the severity cut off point is at 450. Other studies use a severity cut off at CDAI = 300, as there is not much consensus on the matter.

Relevant positive changes in CDAI are those of a fall of at least 70 points.


About the study

The National Cooperative Crohn's Disease Study group collected data from 112 patients with Crohn's disease of the small bowel, colon, or both, in a study led by Best et al. in 1976.

Each patient assessment collected data on 18 predictor variables and about the general wellbeing status of the patient.

The data was run through a multiple regression computer program to derive a predictor equation. Finally, the model was based on 8 selected variables.

In the original study, index values of 150 and below are associated with quiescent disease whilst everything above indicates active disease.


Original source

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):439-44.


Jørgensen LG, Fredholm L, Hyltoft Petersen P, Hey H, Munkholm P, Brandslund I. How accurate are clinical activity indices for scoring of disease activity in inflammatory bowel disease (IBD)? Clin Chem Lab Med. 2005; 43(4):403-11.

Other references

1. Irvine EJ, Feagan B, Rochon J, Archambault A, Fedorak RN, Groll A, Kinnear D, Saibil F, McDonald JW. Quality of life: a valid and reliable measure of therapeutic efficacy in the treatment of inflammatory bowel disease. Canadian Crohn's Relapse Prevention Trial Study Group. Gastroenterology. 1994; 106(2):287-96.

2. Elliott PR, Lennard-Jones JE, Hathway N. Simple index of Crohn's disease activity. Lancet. 1980; 1(8173):876.

Specialty: Gastroenterology

System: Digestive

Objective: Evaluation

Type: Index

No. Of Items: 8

Year Of Study: 1976

Abbreviation: CDAI

Article By: Denise Nedea

Published On: May 22, 2017

Last Checked: May 22, 2017

Next Review: May 22, 2023