Article Index

Case definitions

B.Carruthers (Canada) outlined the New International Criteria for ME. The 2003 Canadian definition has been further refined. The 6 month period is no longer required, but left to clinical judgement at 3 months. Post-Exertional Neuro-immune Exhaustion (PENE) was kept criterial and further articulated. Modifications for paediatric cases have been included. The illness is called ME rather than CFS. The Canadian definition clearly separated out genuine cases, and this new definition can be used clinically and in research and epidemiology.

L.Jason presented work contrasting case definitions. The Fukuda definition has only 4 core symptoms, which do not include post-exertional malaise. But this definition has been used by researchers for over 15 years. He compared this definition with the 2003 ME/CFS Canadian criteria and the older Dowsett ME criteria. His study suggests that the more recent criteria and the ME criteria could be used to identify patients with more homogenous and severe symptomatology and functional impairment.

His second paper describes Data Mining as being a useful tool in aiding the diagnosis of ME/CFS. An objective computer-driven decision is combined with a physician’s medically influenced decision. The Canadian criteria (compared to the Reeves 2005 criteria) were found to have more construct validity and were more accurate, identifying 87% of cases. Post-exertional malaise, neurocognitive symptoms and sleep disorders were not identified as discriminating symptoms with the Reeves criteria.

E.Unger (CDC Atlanta, USA) continued discussions about case definitions. She explained that definitions are not specific to CFS. They are used for epidemiological studies, clinical diagnosis and to determine the biological basis of disease. She stressed the importance of standardization. She asked the question “Will refining lead to a homogenous population?”, and pointed out that heterogeneity is challenging. Phenotypes are imperfect indicators of biology. Case definitions may not be sufficient to discover pathways to pathogenesis. Standardized measures will allow stratification and subtyping.