From ‘Rapid Responses', British Medical Journal, 18 July 2011
Will adopting the Canadian criteria improve the diagnosis of chronic fatigue syndrome?
Esther M Crawley, Consultant Senior Lecturer Alastair Miller, Peter White
University of Bristol
Fiona Godlee suggests that adoption of the Canadian criteria to diagnose chronic fatigue syndrome (CFS) is a reasonable request (1). It may be reasonable, but is probably not practicable. These criteria require the assessment of some 65 discrete symptoms and 14 comorbid conditions, before even considering exclusionary conditions (2); a significant burden on both patients and doctors. More worrying is that “symptoms”, such as ataxia, “palpitations with cardiac arrhythmias”, and “loss of thermostatic stability” count towards the diagnosis, rather than suggesting alternative diagnoses.
All criteria used to diagnose CFS/ME require disabling fatigue lasting between 4 and 6 months; a varying number of symptoms and the exclusion of other illnesses that cause fatigue. There is no evidence that different diagnostic criteria diagnose a different condition (3). There has been a recent attempt to improve the “vaguely worded” Canadian criteria (4), incorporating elements of more orthodox research criteria (5). But these revised criteria still require assessment of too many symptoms of dubious validity. The one advantage of the Canadian criteria over alternative diagnostic criteria is that they require what many would regard as the characteristic feature of CFS, post-exertional malaise (6). This is something that may need incorporating in future definitions to help differentiate CFS from more general fatigue.
Esther Crawley, Consultant Senior Lecturer, University of Bristol, and Clinical lead, Bath specialist paediatric CFS/ME service, Royal National Hospital for Rheumatic Diseases, Upper Borough Walls, Bath BA1 1 RL
Alastair Miller, Consultant Physician, Tropical & Infectious Disease Department, Royal Liverpool University Hospital, Liverpool L7 8XP
Peter D White, Professor of Psychological Medicine, Wolfson Institute of Preventive Medicine, Barts and the London School of Medicine, Queen Mary University of London, EC1A 7BE.
1. Godlee F. Ending the stalemate over CFS/ME. BMJ 2011;342:d3956.
2. Carruthers BM, Jain AK, De Meirleir KL, et al. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Clinical working case definition, diagnostic and treatment protocols. Journal CFS 2003;11:18- 154.
3. National Institute for Health and Clinical Excellence. Clinical guideline CG53. Chronic fatigue syndrome/myalgic encephalomyelitis (or encephalopathy): diagnosis and management. London, NICE, 2007. http://guidance.nice.org.uk/CG53.
4. Jason LA, Evans M, Porter N et al. The development of a revised Canadian myalgic encephalomyelitis chronic fatigue syndrome case definition. Am J Biochem Biotech 2010;6:120-135.
5. Reeves WC, Lloyd A, Vernon SD, et al. International Chronic Fatigue Syndrome Study Group. Identification of ambiguities in the 1994 chronic fatigue syndrome research case definition and recommendations for resolution. BMC Health Serv Res 2003;3(1):25.
6. Cornes O. Commentary: Living with CFS/ME. BMJ 2011;342:d3836.
Competing interests: PDW has done consultancy work for the Departments of Health and Work and Pensions and a re-insurance company.
Published 18 July 2011