Purpose: The main research question is: "Do CFS patients differ from fatigued non-CFS patients with respect to physical, cognitive, behavioral, social, and emotional determinants?" In addition, group differences in relevant outcomes were explored.
Method: Patients who met the Centers for Disease Control (CDC) criteria for CFS were categorized as CFS; these patients were mainly recruited via a large Dutch patient organization. Primary care patients who were fatigued for at least 1 month and up to 2 years but did not meet the CDC criteria were classified as fatigued non-CFS patients. Both groups were matched by age and gender (N = 192 for each group).
Results: CFS patients attributed their fatigue more frequently to external causes, reported a worse physical functioning, more medical visits, and a lower employment rate. The results of a multiple logistic regression analysis showed that patients who believe that their fatigue is associated with more severe consequences, that their fatigue will last longer and is responsible for more additional symptoms are more likely to be classified as CFS, while patients who are more physically active and have higher levels of "all or nothing behavior" are less likely to be classified as having CFS.
Conclusion: A longitudinal study should explore the predictive value of the above factors for the transition from medically unexplained fatigue to CFS in order to develop targeted interventions for primary care patients with short-term fatigue complaints.
Keywords: Behavioral regulation pattern; Chronic fatigue syndrome; Fatigue; Illness representations; Matched case-control; Psychosocial characteristics.