FWIW

This study was funded by the Centers for Disease Control and
Prevention (CDC).
Presumably the money came from the CFS budget.
People from the UK were involved.

I've only just read it but it's unclear to me how much it adds to our
knowledge on CFS.  Much of it is on prolonged fatigue and the linkage
between the prolonged fatigue patients in the study and the CFS
patients is far from clear.  For the CFS patients, they arbitrarily
(it seems to me) restrict it to three countries (the US, Australia and
UK) (33 countries supplied patients for the prolonged fatigue although
admittedly only some of them also have CFS patients (Canada, the
Netherlands, Hong Kong and UAE).

And what the study of prolonged fatigue tells us about CFS (remember
CFS is just a term, to think about this issue, it might be easier to
use another term like ME), is far from clear.  Prolonged fatigue is
fatigue lasting one month or more - no other symptoms are necessary.



Full text at:
http://www.vipbg.vcu.edu/~nathan/publications/Hickie2007.doc

The construct validity of chronic fatigue syndrome is supported by a
multi-national, cross-cultural study.

Ian Hickie, Tracey Davenport, Suzanne Vernon, Rosane Nisenbaum,
William C. Reeves, Andrew Lloyd and the International Chronic Fatigue
Syndrome Study Group*

From the Brain & Mind Research Institute, University of Sydney,
Sydney, NSW, Australia (I.H., T.A.D.), the Viral Exanthems and
Herpesvirus Branch, National Center for Infectious Diseases, Centers
for Disease Control and Prevention, Atlanta, GA, USA (S.V., R.N.,
W.C.R.), and the School of Medical Sciences, University of New South
Wales, Sydney, NSW, Australia (A.L.). Current address: University of
Toronto, Toronto, Canada (RN).

*The researchers who contributed data to this study included:
Professor Gijs Bleijenberg, Dr Sieberen P. van der Werf, Dr Judith B.
Prins (University Medical Centre, Nijmegen, The Netherlands); Dr Paul
M.A. Blenkiron (Bootham Park Hospital, York, United Kingdom);
Professor Dedra Buchwald, Mr Wayne R. Smith (Harborview Medical
Center, Washington, United States); Dr Rachel Edwards, Dr Sean Lynch
(University of Leeds, Leeds, United Kingdom); Professor Laurence J.
Kirmayer, Ms Suzanne S. Taillefer (McGill University, Quebec, Canada);
Dr Sing Lee (Prince of Wales Hospital, Shatin, Hong Kong); Professor
Nicholas G. Martin, Dr Nathan A. Gillespie (Queensland Institute of
Medical Research, Queensland, Australia); Dr Shirley McIlvenny (Sultan
Qaboos University, Sultanate of Oman, United Arab Emirates); Professor
Norman Sartorius, Dr T.B. Ustun (World Health Organization); Dr Petros
Skapinakis (University of Wales, Cardiff, United Kingdom); Professor
Simon Wessely, Dr Trudie Chalder, Dr Matthew Hotoprolonged fatigue, Dr
Chaichana Nimnuan, Ms Bridget Candy, Dr Lucy Darbishire, Dr Leone
Ridsdale (Guy’s, King’s and St Thomas’ School of Medicine, London,
United Kingdom); Professor Peter D. White, Ms Janice M. Thomas (St
Bartholomew’s Hospital, London, United Kingdom); Associate Professor
Kathleen Wilhelm, Mr Dusan Hadzi-Pavlovic, Dr Andrew Wilson
(University of New South Wales, New South Wales, Australia).

Address correspondence to: Professor Ian Hickie, Brain & Mind Research
Institute, P.O. Box M160, Missenden Road, NSW, 2050, Australia or at
ianh@med.usyd.edu.au

ABSTRACT

Background: The development of the international consensus case
definition for chronic fatigue syndrome (CFS) was a major advance for
etiologic and treatment research. However, the construct validity of
CFS and related prolonged fatigue syndromes across cultures and
healthcare settings is still challenged.

Objective: To utilize international epidemiologic and clinical
research datasets to test the construct validity of CFS.

Design: Relevant demographic, symptom, and diagnostic data were
obtained from 14 international study sites in 21 countries, including
33 studies of subjects with fatigue lasting one to six months
(prolonged fatigue), more than six months (chronic fatigue), or CFS.
Common symptom domains were derived by factor analytic techniques and
then compared across cultures, communities, and healthcare settings.

Subjects: Data was obtained from 37,724 subjects  (20,845 women; 57%).
Most data came from population-based studies (n=15,749; 42%), or
studies in primary care (n=19,472; 52%) with only a small proportion
being from referral clinics (n=2,503; n=6%). The sample included 2,013
subjects with chronic fatigue, and 1,958 with CFS.

Results: A five-factor model of the key symptom domains was optimal
and stable across settings. The five factors were labelled:
‘musculoskeletal pain / fatigue’, ‘neurocognitive difficulties’,
‘inflammation’, and ‘sleep disturbance / fatigue’ and ‘mood
disturbance’. These empirically-derived symptom domains overlap
closely with the key components of the diagnostic criteria for CFS.

Limitations: Comparison of the datasets relied upon assumptions
regarding comparable symptom items.

Conclusion: The construct validity of CFS is largely supported by an
empirically-derived factor structure from existing international
datasets. Mood disturbance may be better considered a core, rather
than a co-morbid, component of the syndrome. The CFS construct
consists largely of symptom domains likely to reflect central nervous
system dysfunction