Factor Analysis of the DePaul Symptom Questionnaire: Identifying Core Domains

Abstract

The present study attempted to identify critical symptom domains of individuals with Myalgic Encephalomyelitis (ME) and chronic fatigue syndrome (CFS). Using patient and control samples collected in the United States, Great Britain, and Norway, exploratory factor analysis (EFA) was used to establish the underlying factor structure of ME and CFS symptoms. The EFA suggested a four-factor solution: post-exertional malaise, cognitive dysfunction, sleep difficulties, and a combined factor consisting of neuroendocrine, autonomic, and immune dysfunction symptoms. The use of empirical methods could help better understand the fundamental symptom domains of this illness.

A Brief Questionnaire to Assess Post-Exertional Malaise

“…Similarly, participants rated each symptom’s severity over the past six months on a 5-point Likert scale: 0 = symptom not present , 1 = mild , 2 = moderate , 3 = severe , 4 = very severe . The DSQ has been shown to have good test-retest reliability [7], and the five DSQ PEM items have good internal reliability (α = 0.84).…”

“…Participant responses of PEM duration were coded as: 0 = Not having a problem with energy/fatigue , 1 = 1 h or less , 2 = 2–3 h , 3 = 4–10 h , 4 = 11–13 h , 5 = 14–23 h , and 6 = 24 h or more . Both branching logic questions of symptom exacerbation due to physical activity ( k = 0.84) and symptom exacerbation due to mental activity ( k = 0.74) have good test-retest reliability [7]. …”

“…The NIH/CDC CDE’s PEM working group recognized that the DSQ 5-item first step had some limitations, particularly in terms of the breadth of the symptoms covered, and in its ability to detect PEM triggered by stressors other than physical activity. The next supplemental DSQ question might deal with these concerns, as participants were asked “If you were to become exhausted after actively participating in extracurricular activities, sports, or outings with friends, would you recover within an hour or two after the activity ended?” This item was previously demonstrated as having good test-retest reliability ( k = 0.88) [7]. …”

“…Using a factor analysis, the five DSQ PEM items that the NIH/CDC CDE’s working group recommended as a first step emerged as one factor. This PEM factor had good internal reliability as well as good test-retest reliability [7]. Subsequently these items were included in the DePaul Symptom Questionnaire (DSQ) [8], and factor analyses of this questionnaire have consistently found a PEM factor score [7,9].…”

“…This PEM factor had good internal reliability as well as good test-retest reliability [7]. Subsequently these items were included in the DePaul Symptom Questionnaire (DSQ) [8], and factor analyses of this questionnaire have consistently found a PEM factor score [7,9]. In another study, using these five PEM DSQ items, 97% of the sample ( n = 704) of patients with ME and CFS indicated that they experienced at least one of these PEM symptoms at least half the time and of a moderate or greater severity [10].…”