Chronic Fatigue Syndrome (CFS)

Chronic Fatigue Syndrome

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Case Definition Workshop

May 20-23, 2001

During May 20-23, 2001, the Centers for Disease Control and Prevention (CDC) sponsored a workshop on Issues Related to the Chronic Fatigue Syndrome (CFS) Research Case Definition. This workshop was designed to follow-up on three areas identified at last May's case definition workshop:

Use of the Case Definition: To identify ambiguities (e.g., in symptoms, and exclusionary conditions) in the 1994 research case definition that must be resolved;
Standardization of Classification Instruments: To identify how investigators currently measure variables in the case definition, and which standard instruments should be used in research related to revising the case definition; and
Study Design and Sample Collection in Defined Populations: To identify target populations and study designs to generate data for revising the case definition.

Our intention for the 2001 workshop was to continue the process begun last year. There was agreement that revisions to the CFS research case definition should be based on empiric data. However, population-based data required for revision are not yet available. As an interim measure, participants were asked to identify ambiguities in the 1994 case definition, to identify instruments that provide the best objective measures of multi-dimensional constructs used in the case definition (such as fatigue, cognition, and pain), and to address study designs that will yield empiric data for revision of the case definition.

The first day's objectives were to discuss ambiguous terms, review conditions that would exclude a subject from a research classification of CFS, and review classification instruments. The presentations and discussion made it clear that the research case definition is not refined enough to allow systematic and reproducible application. At least part of the problem is due to the complexity of the symptom group associated with CFS. Fatigue, cognition, pain, sleep disorders, and psychiatric diagnoses are each difficult to measure objectively, and current instruments may be inadequate for the complex integrated processes affected by CFS. There was agreement that CFS case ascertainment would be improved if the research community could formulate guidelines to assist researchers in uniformly applying the case definition. To this end, two working groups were formed to compile the findings of the participants. One group, led by Dr. Klimas, dealt with exclusionary conditions, and the other, led by Dr. Jason, dealt with instruments.

The second day's objective was to consider information to guide the group toward study designs that will yield population-based empiric data required for an improved CFS case definition. Presenters were first asked to review how research in other ill-defined conditions (lupus, depression, and sleep disorders) progressed to identify objective markers of disease. We then discussed model systems (postinfective fatigue from Epstein-Barr virus infection, Q fever, and immune modulation from latent herpesvirus proteins) and information (neuroendocrine and chronobiology) that could guide research about the pathophysiology of CFS. Finally, we closed the day with presentations on integrating multi-source data required for an empiric case definition.

On the third day, we discussed reports by the two working groups. We agreed to prepare a review article critiquing the 1994 CFS Research Case Definition and submit it for publication by July 2001. We also agreed that CDC would take the lead in facilitating communication and 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 by 2003.

Meeting Participants

Invited participants included:

Birgitta Evengard
Huddinge University Hospital, Stockholm, Sweden
Nelson Gantz
Polyclinic Hospital, Harrisburg, PA
Ron Glaser
Ohio State University, Columbus, OH
Christine Heim
Emory University, Atlanta, GA
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
Gundrun Lange
New Jersey Medical School, East Orange, NJ
Andrew Lloyd
University of South Wales, Australia
Andrew Miller
Emory University, Atlanta, GA
Harvey Moldofsky
University of Toronto, Toronto, Canada
Benjamin Natelson
New Jersey Medical School, East Orange, NJ
Thomas J. O'Laughlin
Physical Medicine, Rehabilitation & Electromyography, Fresno, CA
Dimitris Papanicolaou
Emory University, Atlanta, GA
Eng Tan
Scripps Institute, La Jolla, CA
Peter White
St. Bartholomew's Hospital, London, UK