Case Definition Workshop

May 1-3, 2000

During May 1-3, 2000, the Centers for Disease Control and Prevention (CDC) sponsored a small workshop, Issues Related to the Current Chronic Fatigue Syndrome Case Definition, that was attended by approximately 20 invited participants and CDC staff. The meeting's objective was to critically assess current clinical and empirical knowledge concerning the definition of CFS. We identified some of the problems encountered using the 1994 CFS case definition in clinical, research and educational settings. We also considered whether there is both a need for and sufficient data to warrant revision of the CFS case definition. If data were lacking, we wished to identify the nature of the missing information and the kinds of studies that should be designed to gather that information. To these ends, CDC organized the workshop and invited a small group with diverse backgrounds and experience using the chronic fatigue syndrome (CFS) case definition in research, clinical practice, and teaching, in the United States and abroad to participate.

On May 1 and 2, the workshop focused on formal presentations and discussion. Speakers were requested to address three common themes:

1. What have you learned that can be useful in refining the 1994 CFS case definition?
2. What have you not learned by applying the 1994 case definition, due to its limitations/restrictions?
3. What are the remaining unanswered questions in your research?

During Session 1: General Concepts, Dr. Reeves reviewed the 1994 CFS case definition and Dr. Jones presented an overview of fatigue as a concept and its measure/definition. During Session 2: Updated Concepts About CFS, Dr. Lloyd spoke on post-infective fatigue as a model for CFS, Dr. Cleare spoke on using neuroendocrinology and neurochemistry to define CFS, Dr. Evengard reviewed knowledge concerning CFS in Sweden, and Dr. Bleijenberg discussed the features of CFS in the Netherlands. During Session 3: CFS from the Clinician's Point of View, Dr. Klimas addressed the use of the CFS case definition in clinical practice, Dr. Gantz reviewed medical evaluation and classification of CFS, and Ms. Kenney spoke on the CFS case definition and physician training. In Session 4: CFS from the Epidemiologist's Point of View, Dr. Reeves described CDC's use of the case definition in epidemiologic studies, Dr. Jason spoke on methodological challenges of defining CFS, Dr. Nisenbaum spoke on the use of factor analysis to empirically define chronic unwellness and CFS, and Dr. Vernon gave an overview of molecular markers and CFS. Session 5: CFS and Other Illnesses included a talk by Dr. Natelson on Gulf War illness and CFS, a review by Dr. Moldofsky of disordered sleep in fibromyalgia and CFS, and a review by Dr. Abbey of psychiatric disorders and CFS.

On May 3, workshop participants reviewed the presentations and recommended a course of action for future work on the CFS case definition. The participants agreed that it was premature to revise the case definition at this time and that future revisions must be based on data-driven research rather than consensus clinical opinion. Areas of ambiguity in the case definition (such as fatigue severity) must be resolved, appropriate standard methodology must be identified/developed to resolve ambiguities, and additional studies and data analysis must be done to accomplish this objective. Collaboration is critical to resolve these outstanding issues prior to convening a larger meeting to consider whether the case definition should be revised. CDC will take the leadership role in coordinating and facilitating this process. Participants at the May workshop will collaborate to resolve as many issues as possible within 2 years. Individuals who were invited and could not attend the May workshop will also participate. Three working groups were formed: Group 1: Operationalization of the Case Definition, Group 2: Identify Population Groups to Study, and Group 3: Standardize/Operationalize Classification Instruments. The working groups will develop plans with timelines for producing specific recommendations/reports during the next 2 years. The collaborative group will explore options to present an update of their efforts during the American Association of CFS Scientific Meeting in January 2001.

Meeting Participants

Participants included:

• Susan Abbey
  University of Toronto, Toronto, Canada
• Gijs Bleijenberg
  University Hospital Nigmegen, Netherlands
• Anthony Cleare
  St. Thomas School of Medicine, London, UK
• Birgitta Evengard
  Huddinge University Hospital, Stockholm, Sweden
• Nelson Gantz
  Polyclinic Hospital, Harrisburg, PA
• 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
• Andrew Lloyd
  University of South Wales, Australia
• Harvey Moldofsky
  University of Toronto, Toronto, Canada
• Benjamin Natelson
  New Jersey Medical School, East Orange, NJ

Several additional invitees could not attend this meeting because of prior commitments; they will be invited to participate in ongoing activities related to the CFS case definition.

CDC staff who attended the meeting:

• Catherine Campbell
• Ann-Britt Jones
• Kevin Karem
• Rosane Nisenbaum
• Mangalathu Rajeevan
• William C. Reeves
• John Stewart
• Nazareth Subedar
• Elizabeth Unger
• Suzanne Vernon