Rating the severity of a little-studied disease

Microscopic colitis is a common cause of chronic watery diarrhea, especially in older adults. Although incidence of the disease has increased significantly in recent years, microscopic colitis has not been well studied.

The etiology and pathogenesis are not yet entirely clear, and definitions focus on diarrhea to the exclusion of symptoms such as abdominal pain, urgency and weight loss. Furthermore, there has been no validated method for assessing disease severity, making comparisons among treatments difficult.

To help resolve some of these issues, Mayo Clinic gastroenterologist Darrell S. Pardi, M.D., of Mayo Clinic in Minnesota, and colleagues developed a microscopic colitis disease activity index.

"Until now, physicians had no way to objectively and consistently score the severity of a patient's disease beyond counting the number of bowel movements per day," he says. "Our aim was to identify clinical features that are important in the overall assessment of disease activity and arrive at a score that would include diarrhea as well as other symptoms."


Initially, 165 patients at Mayo Clinic in Rochester, Minn. were asked to prospectively assess a number of gastrointestinal symptoms and to provide a global assessment of disease activity at the time of their first visit using a 10-point scale. A physician also scored a physician global assessment (PGA) of the symptoms recorded by the patients. The data were then analyzed to determine which patient symptoms correlated with the physician global assessment and the degree of agreement.


Fourteen patients did not complete the survey. For the remaining 151 patients, five symptoms were strongly associated with the physician assessment. Diarrhea was the most important, followed by incontinence, abdominal pain, nighttime bowel movements and weight loss.

Dr. Pardi says that scores for these symptoms were combined to create an activity index that strongly predicted the PGA.

"This assessment is significant because it strongly correlates a patient's symptoms with the physician's understanding of the severity of microscopic colitis," he says. "Going forward, this will make comparing treatments in clinical trials and case series much easier."


In a follow-up study, Dr. Pardi and his team collected colon biopsies on all enrolled patients. Further analysis will determine if the biopsies add any significant information on disease severity.

"Our aim is to determine whether the efficacy of new treatments in research studies can be determined on the basis of symptoms alone or whether biopsies are also needed. Eliminating biopsies would save considerable time and money and spare patients one more procedure," Dr. Pardi says.