Primary Navigation for the CDC Website
CDC en Español

Search:  

News & Highlights

Chronic Fatigue Syndrome > Publications > Case Defintion Publications >

Identification of ambiguities in the 1994 chronic fatigue syndrome research case definition and recommendations for resolution.

Reeves WC, Lloyd A, Vernon SD, Klimas N, Jason LA, Bleijenberg G, Evengard B, White PD, Nisenbaum R, Unger ER, and the International Chronic Fatigue Syndrome Study Group.
Identification of ambiguities in the 1994 chronic fatigue syndrome research case definition and recommendations for resolution.
BMC Health Services Research 2003;3:25 (The complete electronic version of this article is available at http://www.biomedcentral.com/1472-6963/3/25)

Summary

An International Chronic Fatigue Syndrome Study Group, convened by CDC, has published the first international consensus paper addressing problems in applying the 1994 CFS Research Case Definition and recommending an approach to guide systematic reproducible application of the case definition in research studies. The article should also be helpful to health care professionals who care for persons with CFS.

In 2000, CDC organized an International CFS Study Group comprised of experts in CFS, epidemiology, infectious diseases, endocrinology, immunology, neurology, psychology, psychiatry, biostatistics, and patient advocacy to consider difficulties in applying the current CFS case definition. The Group's first workshop in May 2000 considered how CFS was defined in research studies. Participants agreed that the 1994 International CFS Research Case Definition was not optimal and should be revised and that future revisions should be empirically derived based on data from defined populations. We considered how a case definition should be used for research, what population groups should be studied to revise the case definition, and standardization of classification instruments. The second meeting in June 2001 focused on ambiguities of the 1994 case definition and what specific instruments would provide the best objective measures of the major dimensions of CFS. We met for a third time in May 2002 to discuss how standard instruments measuring the major symptom domains of CFS could be used internationally in clinical research settings. The Group gave final approval to a review article critiquing the CFS case definition, which is under review for publication. At the meeting we agreed upon specific standard instruments that could be uniformly used in international clinical settings to measure fatigue severity, disability, cognition, sleep, psychiatric comorbidity, and other symptoms. We prepared this publication based on the three workshops.

Abstract

Background: Chronic fatigue syndrome (CFS) is defined by symptoms and disability, has no confirmatory physical signs or characteristic laboratory abnormalities, and the etiology and pathophysiology remain unknown. Difficulties with accurate case ascertainment contribute to this ignorance.

Methods: Experienced investigators from around the world who are involved in CFS research met for a series of three day workshops in 2000, 2001 and 2002 intended to identify the problems in application of the current CFS case definition. The investigators were divided into focus groups and each group was charged with a topic. The investigators in each focus group relied on their own clinical and scientific knowledge, brainstorming within each group and with all investigators when focus group summaries were presented. Relevant literature was selected and reviewed independent of the workshops. The relevant literature was circulated via list-serves and resolved as being relevant by group consensus. Focus group reports were analyzed and compiled into the recommendations presented here.

Results: Ambiguities in the current CFS research definition that contribute to inconsistent case identification were identified. Recommendations for use of the definition, standardization of classification instruments and study design issues are presented that are intended to improve the precision of case ascertainment. The International CFS Study Group also identified ambiguities associated with exclusionary and comorbid conditions and reviewed the standardized, internationally applicable instruments used to measure symptoms, fatigue intensity and associated disability.

Conclusion: This paper provides an approach to guide systematic, and hopefully reproducible, application of the current case definition, so that case ascertainment would be more uniform across sites. Ultimately, an operational CFS case definition will need to be based on empirical studies designed to delineate the possibly distinct biological pathways that result in chronic fatigue.

Page last modified on May 8, 2006

Topic Contents

• Topic Contents

Additional Navigation for the CDC Website

“Safer Healthier People”
 Centers for Disease Control and Prevention, 1600 Clifton Rd, Atlanta, GA 30333, USA
Tel: 404-639-3311  /  Public Inquiries: (404) 639-3534  /  (800) 311-3435