A COMPARISON OF CASE DEFINITIONS OF CHRONIC FATIGUE SYNDROME

We compared three case definitions of chronic fatigue syndrome (CFS) a pplied to patients followed in CFS clinics at two institutions. All pa tients had debilitating fatigue without apparent etiology; patients wi th medical conditions associated with chronic fatigue and with major p sychiatric disorders were stratified and presented separately. Patient s were classified according to whether they met case definitions devel oped by a Centers for Disease Control and Prevention (CDC) Working Gro up, a British group, or an Australian group. When findings for 805 pat ients followed at the two clinics were combined, 61% met the CDC crite ria, 55% met the British criteria, and 56% met the Australian criteria ; these proportions were relatively similar at both sites. In addition , similar laboratory abnormalities were found for all case groups and for fatigued patients who met none of the three case definitions. Thes e data suggest that more inclusive case definitions may be superior.