This Crohn’s Disease Activity Index (CDAI) calculator assesses disease severity based on general symptoms, haematocrit and weight factors. Below the form there is in depth information on how to perform the calculations and adjustments in this bowel disease activity score.
How does the Crohn’s Disease Activity Index (CDAI) calculator work?
This health tool is used to assess disease severity based on quantification of symptoms from patients. Mostly used as a research tool in medication studies, it defines a severity stage and outlines the cut off for Crohn’s disease remission.
Developed in 1976, the CDAI appeals to a diary of symptoms for the past 7 days concerning stool and general health as well as to a series of clinical symptoms and laboratory determinations such as the haematocrit.
The Crohn’s Disease Activity Index (CDAI) calculator outlines the 8 factors that are each weighted by an adjustment factor, then to be summed in the final score. The factors are explained below:
■ Liquid stools – cumulative number of liquid or soft stools over the last seven days. The sum obtained is multiplied by a factor of x2.
■ Abdominal pain – daily assessment on an ordinal scale from 0 (no pain) to 3 (severe pain). The 7 ratings are added together to generate a preliminary score which is then adjusted by a score x 5 factor.
■ General well being – offers a daily assessment on an ordinal scale from 0 to 4, where 0 means well and 4 means terrible. The 7 day ratings are added together to generate a preliminary score which is then adjusted by a score x 7 factor.
■ Extra-intestinal complications – there are several examples and the user is asked to select any that apply. Each selected counts as 1 point which is then adjusted by a score x 20 factor.
■ Diarrhea treatment – if under treatment with Lomotil, Loperamide or Opiates, adjustment factor of +30 is applied.
■ Abdominal mass – presence of an abdominal mass: if none = 0, if questionable = 2, if definite = 5. Then an adjustment factor of score x10 is applied.
■ Haematocrit in % – applies a gender differentiated formula: Males = (47 – user hct) x 6, Females = (42 – user hct) x 6.
■ Weight – requires current body weight and applies the following formula: 100 x (1 – current weight/standard weight).
The following table summarizes the 8 items in the disease index, the preliminary results and the factors that are applied for each:
|CDAI item||Points/ Value||Adjustment factor|
|Liquid stools||Sum for last 7 days||x2|
None = 0
Low Intermediate = 1
High Intermediate = 2
Severe = 3
|Sum of ratings for last 7 days||x5|
General well being
Well = 0
Low Intermediate = 1
High Intermediate = 2
High = 3
Terrible = 4
|Sum of ratings for last 7 days||x7|
|Extra-intestinal complications||1 point for each complication||x20|
|Diarrhea treatment||1 point if under treatment||x30|
None = 0
Questionable = 2
Definite = 5
|Number of points of selection||x10|
|Haematocrit in %||Male = (47 - user value)||x6|
|Female = (42 - user value)|
|Weight||100 x (1 - current weight/standard weight)|
It is important to note that while this bowel disease index gauges the progress or lack of progress in case of individual patients and has been validated as gold standard in assessing disease severity, it has little to none prognostic value.
The only note in this regard in the original study is that about remission results, “generally speaking, CDAI scores below 150 indicate a better prognosis than higher scores”.
In subsequent studies, the remission value of 150 has been adjusted to values between 200 and 250, depending on individual preference of researchers.
Therefore, the way to use CDAI as progress prediction tool is to subjectively compare values from one evaluation to another, not rely on singular results.
The Harvey Bradshaw Index is a simplified version of the CDAI and beside that, there is the Inflammatory Bowel Disease Questionnaire (IBDQ) that focuses more on the effect of the symptoms on the patient’s quality of life.
CDAI score interpretation
The scores obtainable in the disease activity index range between 0 and 600. While the main association is that of scores below 150 indicating remission of the disease, the following table aims to introduce ranges of severity.
The main rule remains though that the higher the score, the more severe the disease stage. Some studies correlate the cut off for severity with a CDAI of 300, different from the one presented below. To this date there is not much consensus on this.
Response cut off is defined in most research studies of Crohn’s disease medication as a change in CDAI (positive change – fall of index value) of more than 70 points.
|CDAI score||Crohn’s disease severity|
|150 – 220||Mild|
|221 – 450||Moderate to severe|
1) Irvine EJ, Feagan B, Rochon J, Archambault A, Fedorak RN, Groll A, Kinnear D, Saibil F, McDonald JW. (1994) 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; 106(2):287-96.
2) Best WR, Becktel JM, Singleton JW, Kern F Jr. (1976) Development of a Crohn's disease activity index. National Cooperative Crohn's Disease Study. Gastroenterology; 70(3):439-44.
3) Elliott PR, Lennard-Jones JE, Hathway N. (1980) Simple index of Crohn's disease activity. Lancet; 1(8173):876.08 May, 2016