Crohn’s disease presents with so many patterns, locations, complications and can also coexist with other diagnoses such as irritable bowel symptoms, that classifying disease of one patient and then comparing that patient to others is not always possible. As physicians, we try to establish severity on objective clinical findings, and then asses the global impact on the patient’s quality of life. While there are several indices of disease activity that have been used for the purposes of research studies, these are not often used routinely in clinical practice. In fact no “gold standard” indicator of clinical disease has been established in guidelines.
The majority of clinical trials have used the Crohn’s Disease Activity Index (CDAI) to assess therapeutic outcomes. The CDAI consists of eight factors (clinical symptoms during the prior week: number of liquid stools, abdominal pain, general well being and objective findings: presence of complications, abdominal mass, blood counts and need for Lomotil or opiates for diarrhea) which are weighted. Calculators are available online. Another index, The Harvey-Bradshaw index consists only of clinical parameters: general well being, abdominal pain, number of liquid stools, abdominal mass, and complications. These indexes are rarely used in clinical practice other than for classifying patients for research purposes. Studies have shown that indexes are cumbersome to use in practice and require patients to remember several days worth of symptoms, are limited due to use of subjective variables and have high interobserver variability: the results can vary widely depending on the person filling the questionnaires.
Working definitions, used more for the purposes of research per the most recent Crohn’s Disease Practice Guidelines are as follows:
-Symptomatic remission CDAI <150 : asymptomatic and have no active disease by objective evaluation. These patients are those who have responded to medical therapy or surgical therapy without any signs of active disease. The goal is for these patients to also have no microscopic findings of active disease on endoscopic biopsies. Steroid dependent patients are NOT considered to be in remission.
-Mild to Moderate Disease CDAI 150-220: able to tolerate oral nutrition without weight loss or dehydration, and do not have signs of severe abdominal pain, painful mass, obstruction or systemic findings. They have continued findings of active disease endoscopically, by labs or imaging.
-Moderate to Severe Disease CDAI 220-450: patients who have failed to respond to treatment - or have prominent symptoms including fever, weight loss, constant abdominal pain, significant anemia, more pronounced endoscopic and imaging findings.
-Severe/Fulminant Disease CDAI >450: patients with persistent symptoms despite treatment and corticosteroids, or patients with high fevers, persistent vomiting, intestinal obstruction, or severe disease complications such as abscess.
BOTTOM LINE
Severity is distinguished clearly more for research purposes than practical clinical use. As physicians our goal is to find treatments appropriate to each patient in hopes of improving their quality of life and decreasing the long term risks associated with their disease – no matter where on the spectrum of severity a patient may fall.
