Diagnosis of Chronic Fatigue Syndrome in Adolescents

Diagnostic labels as Chronic Fatigue Syndrome (CFS), Myalgic Encephalomyelitis (ME) and Systemic Exertion Intolerance Disease (SEID) represent different approaches to the enigmatic phenomenon of long-lasting unexplained fatigue. More than 20 case definitions/diagnostic criteria for CFS/ME/SEID exist (further referred to as CFS). All are based on subjective symptom reports, and the details of symptom requirement vary considerably. No one has been thoroughly validated. The overarching aim of the thesis was to investigate diagnostic criteria for CFS by: 1) Assess the descriptive, prognostic and construct validity of the Canadian Consensus Criteria (CCC) and the SEID-criteria in adolescent CFS patients, utilizing objectively defined disease markers. 2) Perform a cluster analysis on disease markers within a widely defined group of fatigued adolescents in an attempt to reveal subgroups not visible at the phenotypical level. The present thesis shows that adolescent CFS patients fulfilling the CCC or SEID-criteria do not differ from adolescent CFS patients diagnosed according to broad diagnostic criteria regarding neuroendocrine, cardiovascular, inflammatory, infectious or cognitive variables. Furthermore, there appears to be no distinct subgroups within the overarching CFS label. These findings question the validity of the CCC and SEID-criteria, and more fundamentally question the rationale of sub-classifying chronically fatigued patients based on clinical symptoms. Rather, the results seem to suggest that all patients with an unexplained chronic fatigue may be seen as one entity in a qualitative sense, albeit with individual, quantitative differences regarding symptom severity, functional impairments and pathophysiological aberrations