In the United States, the average doctor’s appointment lasts around 18 minutes, and the average primary care doctor sees about 20 patients a day. That can be enough time if a patient has, say, a clear case of shingles. But the encounter becomes far more challenging when a patient arrives complaining of symptoms with no obvious cause.
Doctors have roughly 17,000 diagnostic disease categories to choose from, most of which share some of the same 150 to 200 common signs and symptoms. A headache could be a symptom for some 300 diseases and chest pain could be a symptom of 25. A symptom like fatigue could have countless possible causes. “There are several sources of frustration for a doctor when a patient walks in and says, ‘I just have not had my usual energy, and I’m not able to function at home or at work the way I used to,’” said Dr. Anthony Komaroff, a leading expert in myalgic encephalomyelitis/chronic fatigue syndrome, or M.E./C.F.S., at Harvard.