LAUSR

Abstract Purpose Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is an illness characterized by a variety of symptoms including post-exertional malaise, unrefreshing sleep, and cognitive impairment. A variety of case definitions (e.g., the Canadian Consensus Criteria (CCC), the Myalgic Encephalomyelitis International Consensus Criteria (ME-ICC), and the Institute of Medicine (IOM) criteria) have been used to diagnose patients. However, these case definitions are consensus-based rather than empirical. Materials and methods The aim of the current study was to evaluate the validity of the aforementioned case definitions by factor analyzing a large, international sample (N = 2308) of ME/CFS symptom data. We performed primary and secondary exploratory factor analyses on the DePaul Symptom Questionnaire's 54-item symptom inventory. These results were compared to the CCC, the ME-ICC, and the IOM criteria. Results We identified seven symptom domains, including post-exertional malaise, cognitive dysfunction, and sleep dysfunction. Contrary to many existing case criteria, our analyses did not identify pain as an independent factor. Conclusions Although our results implicate a factor solution that best supports the CCC, revisions to the criteria are recommended. Implications for rehabilitation ME/CFS is a chronic illness with no consensus regarding case diagnostic criteria, which creates difficulty for patients seeking assistance and disability benefits. The current study compared three commonly used case definitions for ME/CFS by factor analyzing symptomological data from an international sample of patients. Our results suggest three primary and four secondary symptom domains which differed from all three case definitions. These findings could help reduce barriers to care for those disabled with ME/CFS by guiding the development of an empirically-based case definition.