title: Case definitions integrating empiric and consensus perspectives.
abstract: BACKGROUND
  There has been considerable controversy regarding how to name and define the illnesses known as myalgic encephalomyelitis (ME) and chronic fatigue syndrome (CFS). The IOM report has proposed a new clinical criteria and name for this illness, but aspects of these recommendations have been scrutinized by patients and scientists.
  
  
  OBJECTIVE
  It is possible that both empiric and consensus approaches could be used to help settle some of these diagnostic challenges. Using patient samples collected in the United States, Great Britain, and Norway (N=556), the current study attempted to categorize patients using more general as well as more restricted case definitions.
  
  
  RESULTS
  Overall, the outcomes suggest that there might be four groupings of patients, with the broadest category involving those with chronic fatigue (N=62), defined by 6 or more months of fatigue which can be cannot be explained by medical or psychiatric conditions. A second category involves those patients that have chronic fatigue that can be explained by a medical or psychiatric condition (N=47). A third category involves more specific criteria that have been posited both by the IOM report, a Canadian Clinical Case criteria, a ME-ICC criteria and a more empiric approach. These efforts have specified domains of substantial reductions of activity, post-exertional malaise, neurocognitive impairment, and sleep dysfunction (N=346). Patients with these characteristics were more functionally impaired than those meeting just chronic fatigue criteria,p< .05. Finally, those meeting even more restrictive ME criteria proposed by Ramsay, identified a smaller and even more impaired group,p< .05.
  
  
  CONCLUSIONS
  The advantages of using such empirical and consensus approaches to develop reliable classification and diagnostic efforts are discussed.
authors.affiliation: Center for Community Research, DePaul University, Chicago, IL USA.
authors.forename: Leonard A
authors.initials: LA
authors.lastname: Jason
authors.affiliation: Center for Community Research, DePaul University, Chicago, IL USA.
authors.forename: Stephanie
authors.initials: S
authors.lastname: McManimen
authors.affiliation: Center for Community Research, DePaul University, Chicago, IL USA.
authors.forename: Madison
authors.initials: M
authors.lastname: Sunnquist
authors.affiliation: Center for Community Research, DePaul University, Chicago, IL USA.
authors.forename: Abigail
authors.initials: A
authors.lastname: Brown
authors.affiliation: Center for Community Research, DePaul University, Chicago, IL USA.
authors.forename: Jacob
authors.initials: J
authors.lastname: Furst
authors.affiliation: Newcastle University.
authors.forename: Julia L
authors.initials: JL
authors.lastname: Newton
authors.affiliation: Oslo University Hospital.
authors.forename: Elin Bolle
authors.initials: EB
authors.lastname: Strand
keywords: case definition; chronic fatigue syndrome; myalgic encephalomyelitis