The planning, implementation and publication of a complex intervention trial for chronic fatigue syndrome: the PACE trial

The PACE trial was a four-arm trial of specialist medical care, compared with specialist medical care with a supplementary therapy: adaptive pacing therapy, cognitive–behavioural therapy or graded exercise therapy, for patients with chronic fatigue syndrome. The trial found that both cognitive–behavioural and graded exercise therapies were more effective than either of the other two treatments in reducing fatigue and improving physical disability. This paper describes the design, conduct and main results of the trial, along with a description of the challenges that had to be overcome in order to produce clear answers to the clinically important questions the trial posed.