Chronic Fatigue Syndrome: The Need for Subtypes

Abstract

Chronic fatigue syndrome (CFS) is an important condition confronting patients, clinicians, and researchers. This article provides information concerning the need for appropriate diagnosis of CFS subtypes. We first review findings suggesting that CFS is best conceptualized as a separate diagnostic entity rather than as part of a unitary model of functional somatic distress. Next, research involving the case definitions of CFS is reviewed. Findings suggest that whether a broad or more conservative case definition is employed, and whether clinic or community samples are recruited, these decisions will have a major influence in the types of patients selected. Review of further findings suggests that subtyping individuals with CFS on sociodemographic, functional disability, viral, immune, neuroendocrine, neurology, autonomic, and genetic biomarkers can provide clarification for researchers and clinicians who encounter CFS' characteristically confusing heterogeneous symptom profiles. Treatment studies that incorporate subtypes might be particularly helpful in better understanding the pathophysiology of CFS. This review suggests that there is a need for greater diagnostic clarity, and this might be accomplished by subgroups that integrate multiple variables including those in cognitive, emotional, and biological domains.

Chronic fatigue syndrome (CFS) symptom-based phenotypes in two clinical cohorts of adult patients in the UK and The Netherlands

“…Of the dozen or so CFS phenotype studies published since 1995 (Jason et al, 2005), only one had a sample size approaching ours: a multi-country study by Hickie et al which was based on a sample of 37724 people, of whom 1958 were formally diagnosed with CFS (Hickie et al, 2009). A twin registry-based study in Sweden was based on a sample of 5,330 , but only 732 (2.4%) were classified as having a CFS-like illness .…”

“…Heterogeneity in the symptom profile of CFS can be confusing for clinicians, fuelling debate over diagnostic criteria, and posing an obstacle to biomedical research that aims to find biomarkers of CFS (Jason et al, 2005). Several studies have investigated heterogeneity (phenotypes) in adult (Hickie et al, 2009, Hickie et al, 1995, Janal et al, 2006, Sullivan et al, 2002, Wilson et al, 2001 and paediatric (May et al, 2010) CFS patients.…”

The Epigenetic Landscape of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Deciphering Complex Phenotypes

“…Through the integration of published and publicly available biological and clinical data of diseases with similar clinical features, subsets that contain patients with different complex diseases will help identify the biological differences that are related to symptoms that are shared among patients. These comparisons will establish the biological differences that are unique to ME/CFS pathophysiology, assisting in refining diagnostic criteria and developing targeted therapeutics [8].…”

“…The potential utility of subtyping in ME/CFS in a manner that integrates phenotypic and biological data has been recognized for some time (e.g., [8]). ME/CFS immune subtypes have been described based on gene expression differences [9], dichotomous T cell GC sensitivity [13] and the varying efficacy of B cell therapy in relation to treatment [9].…”

Subgrouping in Chronic Fatigue Syndrome Based on Actigraphy and Illness Severity

“…Several research groups emphasized the importance of finding distinct subgroups within the CFS population [4,5]. The group that developed the International criteria for CFS stressed the need to reduce heterogeneity and encouraged researchers to develop stratification strategies that would help to identify distinctive subtypes [4].…”