A study of chronic fatigue syndrome, published last month in The Lancet, has highlighted how competing case definitions for illnesses and syndromes can lead to confusion rather than clarification — what you see depends on who’s doing the looking — and has stoked a fierce debate among researchers and patient advocates on both sides of the Atlantic as noted in this New York Times article.
“If you recognize something is happening, you need a case definition so you can count it,” said Andrew Moss, an emeritus professor of epidemiology at U. C. San Francisco and an early AIDS investigator. “You need to know whether the numbers are going up or down, or whether treatment and prevention work. And if you have a bad case definition, then it’s very difficult to figure out what’s going on.”
Once a disease can be diagnosed reliably through lab tests, creating an accurate case definition becomes easier. But when an ailment has no known cause and its symptoms are subjective — as with chronic fatigue syndrome, fibromyalgia, and other diseases whose characteristics and even existence have been contested — competing case definitions are almost inevitable.
What does this mean for the patient? Well, quite a lot. As the article notes, treatments could easily vary depending upon which diagnostic measurements a physician were using. In the case of chronic fatigue, some researchers believe that the syndrome is a psychological condition and patients would benefit from exercise. Other researchers, however, are deeply convinced it is a viral disease and note that the exercise therapy advised by the Lancet study can cause major relapses in people with chronic fatigue syndrome — a claim supported by some patient surveys. Read more…