Case Definition Workshop

May 21-22, 2002

During May 21-22, 2002, the Centers for Disease Control and Prevention (CDC) sponsored the Third Annual Case Definition Workshop on Chronic Fatigue Syndrome. This workshop was designed to continue a process established in two previous workshops on the same issue. Participants at the first workshop (May 2000) agreed that the 1994 International CFS Research Case Definition was not optimal, that it should be revised, and that future revisions should be based on empirically derived data (if possible from defined populations). Three groups were formed to discuss the following issues: how a case definition should be used for research; how population groups should be identified for studies and how classification instruments should be standardized.

The second meeting (June 2001) focused on ambiguities of the 1994 case definition and on what instruments would provide the best objective measures of the major dimensions of CFS. We agreed to prepare a review article critiquing the 1994 case definition. We also agreed that CDC would take the lead in facilitating communication about the CFS case definition and in forming an International Collaborative Group to test standard instruments and collect data that could be used to propose an empiric data-based revision to the case definition.

The overall objective of the third meeting was to maintain the momentum of the International Collaborative Group and continue the work to more precisely define CFS. The specific aim was to discuss how standard instruments measuring the major symptom domains of CFS could be used internationally in clinical research settings. During the meeting, three working groups sought to develop strategies to address the following issues:

• A means by which standard instruments can be uniformly applied in different clinical and cultural settings.
• Specific standard instruments that would optimally measure fatigue severity, disability, cognition, sleep, other symptoms, and psychiatric comorbidity and could be uniformly used in international clinical settings.
• Analytic procedures that would identify symptom dimensions among persons with CFS and other unexplained chronically fatiguing illnesses in international clinical research settings and would define the variability of symptom dimensions manifest by different patient populations. This group also discussed study designs necessary to accomplish analysis.

On the basis of these discussions, CDC is planning to analyze data from international studies of CFS to determine similarities in patterns of symptoms between different localities and to better focus an international collaborative effort to empirically define CFS. In conjunction with this analysis, CDC is beginning to plan an international pilot study that will use instruments recommended by the International Collaborative Group to identify symptom dimensions among persons with unexplained chronic fatigue; determine the variability of symptom dimensions across the sites; measure the associations between symptom dimensions and other health constructs; and determine the feasibility of conducting an international multicenter study of unexplained chronic fatigue by using an international chronic fatigue research network.

Meeting Participants

Participants included:

• Gijs Bleijenberg
  University Medical Center Nijmegen, Netherlands
• Dedra Buchwald
  University of Washington, Seattle, WA
• Birgitta Evengard
  Huddinge University Hospital, Stockholm, Sweden
• Nelson Gantz
  Polyclinic Hospital, Harrisburg, PA
• Christine Heim
  Emory University, Atlanta, GA
• Ian Hickie
  University of New South Wales, Australia
• Gail Ironson
  University of Miami, Miami, FL
• Leonard Jason
  DePaul University, Chicago, IL
• James Jones
  National Jewish Medical Center, Denver. CO
• K. Kimberly Kenney
  CFIDS Association of America, Charlotte, NC
• Nancy Klimas
  University of Miami/VA Medical Center, Miami, FL
• Hirohiko Kuratsune
  Osaka University, Osaka, Japan
• Andrew Lloyd
  University of New South Wales, Australia
• Harvey Moldofsky
  University of Toronto, Toronto, Canada
• Benjamin Natelson
  New Jersey Medical School, East Orange, NJ
• Vicki Walker
  CFIDS Association of America, Charlotte, NC
• Peter White
  St. Bartholomew's Hospital, London, UK

CDC participants were:

• Rosane Nisenbaum
• Mangalathu Rajeevan
• William C. Reeves
• John Stewart
• Elizabeth Unger
• Suzanne Vernon