We selected participants in accordance with Oxford criteria for chronic fatigue syndrome.
11 These criteria require fatigue to be the main symptom, accompanied by significant disability, in the absence of an exclusionary medical or
psychiatric diagnosis(psychosis,
bipolar disorder,
substance misuse, an organic brain disorder, or an eating disorder).
11 All participants were medically assessed by the specialist clinic doctors to exclude alternative diagnoses.
2,12 Research assessors used the structured clinical interview from the
Diagnostic and Statistical Manual of Mental Disorders IV to diagnose exclusionary and comorbid
psychiatric disorders (ie, mood and anxiety disorders).
10,14
Other eligibility criteria consisted of a bimodal score of 6 of 11 or more on the Chalder fatigue questionnaire
15 and a score of 60 of 100 or less on the short form-36 physical function subscale.
16 11 months after the trial began, this requirement was changed from a score of 60 to a score of 65 to increase recruitment.
We excluded patients who were younger than 18 years or at significant risk of self-harm, unable to attend hospital appointments, unable to speak and read English, had medical needs that made participation inappropriate, had previously received a trial treatment for their present illness at a PACE trial clinic (we initially excluded anyone who had received a trial treatment, but found the nature of treatment given elsewhere hard to establish).
10 Participants were also assessed by international criteria for chronic fatigue syndrome,
12 requiring four or more accompanying symptoms, and the London criteria
13for myalgic encephalomyelitis (version 2), requiring postexertional fatigue, poor memory and concentration, symptoms that fluctuate, and no primary
depressive or anxiety disorder (interpreted as an absence of any such disorder).