Proper Diagnostic Criteria for ME/CFS/CFIDS? Canadian Dr. Byron Hyde (lecturing in Brisbane Australia this week) is very critical of the CDC’s ‘catch-all’ definition of “chronic fatigue syndrome” vs. the Nightingale definition of ME. He says most people in Canada, US, and UK he has seen with “gradual onset” (vs acute onset) CFS really have been misdiagnosed and have some other, “undiagnosed major illness.” I’m not sure if I’m gradual onset. What is your thinking on this? Reply: I agree. Often many of the signs and symptoms of CFS overlap with other chronic illnesses, making diagnosis more difficult. However, there also appear to be various subcategories of CFS, which may depend on a number of factors, so it is not clear whether a broad or narrow definition of CFS/ME is more useful. Certainly for scientific studies the narrow definition is more useful, but it may not be very practical in the clinic.