Objectives: The present study sought to validate a comprehensive self-report measure of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) symptomatology to aid in clinical and research assessment.
Method: Exploratory factor analysis (EFA) was used to establish the underlying factor structure of the DePaul Symptom Questionnaire (DSQ) (Jason, Evans, et al., 2010) using a well-characterized sample of individuals (92.6% met the Fukuda et al. criteria (1994) and/or the Clinical Canadian Criteria (Carruthers et al., 2003)), and this structure was then tested on a less stringently recruited sample of individuals utilizing a confirmatory factor analysis (CFA). Convergent and discriminant validity of the DSQ were also examined utilizing alternative measures of symptomatology and functioning.
Results: A 3-factor solution was found using EFA (Neuroendocrine, Autonomic & Immune Dysfunction; Neurological/Cognitive Dysfunction; Post-Exertional Malaise) and the fit of this factor structure was adequate for the second sample.
Discussion: The DSQ is a valid measure of ME/CFS symptomatology. The emergent factors were consistent with previous literature on symptom clusters, and convergent and discriminant validity were established.
Keywords: DePaul Symptom Questionnaire; case definition; chronic fatigue syndrome; diagnostic criteria; myalgic encephalomyelitis.