FUNCTIONAL STATUS IN PATIENTS WITH CHRONIC FATIGUE SYNDROME, OTHER FATIGUING ILLNESSES, AND HEALTHY-INDIVIDUALS

BACKGROUND: Chronic fatigue syndrome (CFS) is a condition that may be associated with substantial disability. The Medical Outcomes Study Sho rt-Form General Health Survey (SF-36) is an instrument that has been w idely used in outpatient populations to determine functional status. O ur objectives were to describe the usefulness of the SF-36 in CFS pati ents and to determine if subscale scores could distinguish patients wi th CFS from subjects with unexplained chronic fatigue (CF), major depr ession (MD), or acute infectious mononucleosis (AIM), and from healthy control subjects (HC). An additional goal was to ascertain if subscal e scores correlated with the signs and symptoms of CFS or the presence of psychiatric disorders and fibromyalgia. DESIGN: Prospectively coll ected case series. SETTING: Patients with CFS and CF were seen in a un iversity-based referral clinic and had undergone a complete medical an d psychiatric evaluation. Other study subjects were recruited from the community to participate in research studies. PARTICIPANTS: The study included 185 patients with CFS, 246 with CF, 111 with AIM, and 25 wit h MD. There were 99 HC subjects. MEASURES: The SF-36 and a structured psychiatric interview were used. The SF-36 contains 8 subscales: physi cal, emotional, social, and role functioning, body pain, mental health , vitality, and general health-and a structured psychiatric interview. RESULTS: Performance characteristics (internal reliability coefficien ts, convergent validity) of the SF-36 were excellent. A strikingly con sistent pattern was found for the physical functioning, role functioni ng, social functioning, general health, and body pain subscales, with the lowest scores in CFS patients, intermediate scores in AIM patients , and the highest scores in the HC subjects. The CFS patients had sign ificantly lower scores than patients with CF alone on the physical fun ctioning (P less than or equal to 0.01), role functioning (P less than or equal to 0.01), and body pain (P less than or equal to 0.001) subs cales. The emotional functioning and mental health scores were worst a mong those with MD. The presence of fibromyalgia, being unemployed, an d increasing fatigue severity all were associated with additional func tional limitations across multiple functional domains, with increasing fatigue appearing to have the greatest effect. CONCLUSIONS: The SF-36 is useful in assessing functional status in patients with fatiguing i llnesses. Patients with CFS and CF have marked impairment of their fun ctional status. The severity and pattern of impairment as documented b y the SF-36 distinguishes patients with CFS and CF from those with MD and AIM, and from HC, but does not discriminate between CF and CFS.