The Activity Index (AI) is a quantitative and objective measure of inflammatory activity in patient's with Crohn's disease. This can be used to assess the patient initially and to monitor the patient's course over time.
Parameters used for the index:
(1) serum albumin
(2) erythrocyte sedimentation rate
(3) Quetelet's index
(4) abdominal mass
(5) sex
(6) body temperature
(7) stool consistency
(8) history of bowel resection
(9) presence of extraintestinal lesions
|
Parameter |
Finding |
Value |
|
serum albumin |
in g/L |
serum value |
|
erythrocyte sedimentation rate |
in mm after 1 hour |
ESR |
|
Quetelet index (body mass index), modified |
(10 * (weight in kg)) / ((height in m)^2) |
index value |
|
abdominal mass |
no |
1 |
|
|
dubious |
2 |
|
|
diameter < 6 cm |
3 |
|
|
diameter 6-12 cm |
4 |
|
|
diameter > 12 cm |
5 |
|
sex |
male |
1 |
|
|
female |
2 |
|
temperature in °C |
afebrile |
37 |
|
|
febrile |
mean for evening temperature last 7 days |
|
stool consistency |
well-formed |
1 |
|
|
soft, variable |
2 |
|
|
watery |
3 |
|
resection |
no |
1 |
|
|
yes |
2 |
|
extraintestinal lesions |
no |
1 |
|
|
yes |
2 |
where:
• The Quetelet's index parameter is modified by use a factor of 10 times the weight as (10 * (body weight in kilograms)).
|
Parameter |
Regression Coefficient |
|
serum albumin |
-5.48 |
|
ESR |
0.29 |
|
Quetelet index |
-0.22 |
|
abdominal mass |
7.83 |
|
sex |
-12.3 |
|
temperature |
16.4 |
|
stool consistency |
8.46 |
|
resection |
-9.17 |
|
extraintestinal lesions |
10.7 |
|
constant |
-209 |
activity index (AI) =
= SUM((regression coefficient) * (parameter value))
Interpretation:
• minimum value in the original paper was around 50 (variable due to serum albumin, body mass index and ESR).
• maximum value in the original paper was around 300 (variable due to albumin, body mass index, ESR and temperature)
|
Activity Index |
Inflammatory Activity |
|
<= 100 |
no activity |
|
100 - < 150 |
slight |
|
150 - 210 |
moderate |
|
> 210 |
severe |
where:
• The interpretation in the article is ambiguous for 150, as the breakpoints for slight inflammatory activity are 100-150 and for moderate are 150-200. I have opted to use a value of 150 to indicate moderate activity.
Specialty: Gastroenterology
