To exercise or not to exercise in chronic fatigue syndrome?

To the Editor: The claim in Lloyd’s editorial1 that “the criteria for diagnosis are well accepted internationally” ignores the recent publication of the Canadian consensus guidelines for the diagnosis and management of myalgic encephalomyelitis/chronic fatigue syndrome,2 which were sponsored by Health Canada and written by an international group of well published researchers. The Canadian definition of chronic fatigue syndrome (CFS) requires the concurrent presence for six months of fatigue, post-exertional fatigue, sleep dysfunction, pain (including headaches) and neurological/cognitive manifestations, as well as at least one symptom from two of autonomic, neuroendocrine and immune manifestation categories (pp 12–13). These requirements add clinical specificity to the Fukuda criteria and exclude subjects who may have chronic fatigue for other reasons, such as psychiatric disorder without multiple physical symptoms.