Abstract
A diagnosis of chronic fatigue syndrome (CFS) requires the exclusion of other known fatigue-related diseases and requires compliance with a clinical definition. The patient set derived by this process is heterogeneous in its polysymptomatic presentation and has proved very difficult to study clinically and scientifically. Our laboratory has been involved in research to evaluate changes in biochemical and physiological homeostasis which might occur in CFS patients. The studies have included investigating urinary excretion, blood lipids, immunology, organochlorine pesticides and microbiology. All these research projects indicated that the CFS patients have multiple anomalies in their homeostasis. The multivariate cluster analyses of these data sets indicated that different types of CFS patient could be characterized on the basis of similarities in metabolite profiles. The measured changes in metabolite composition were strongly associated with symptom incidence and severity, suggesting that these subtle patterns of metabolism have a strong influence on CFS symptom presentation.