Myalgic Encephalomyelitis Chronic Fatigue Syndrome

LONDON CRITERIA FOR M.E.

EG Dowsett, E Goudsmit, A Macintyre, C Shepherd, et al., London criteria for M.E., Report from The National Task Force on Chronic Fatigue Syndrome (CFS), Post Viral Fatigue Syndrome (PVFS), Myalgic Encephalomyelitis (ME). Westcare,
1994, pp. 96-98.

Version 2
THE 'LONDON' CRITERIA

DIAGNOSTIC CRITERIA FOR THE SELECTION OF SUBJECTS FOR RESEARCH INTO M.E. / PVFS

These three criteria must all be present for a diagnosis of M.E./PVFS to be made. If any of these are not present the volunteer research subject should not be used for the purpose of research into M.E./PVFS and an alternative diagnosis should be keenly sought.

a) Exercise-induced fatigue precipitated by trivially small exertion -physical or mental - relative to the patient's previous exercise tolerance.

b) Impairment of short-term memory and loss of powers of concentration, usually coupled with other neurological and psychological disturbances such as emotional lability, nominal dysphasia, disturbed sleep patterns, dysequilibrium or tinnitus.

c) Fluctuation of symptoms, usually precipitated by either physical or mental exercise (see b) above.

These symptoms should have been present for at least 6 months and should be ongoing.

A VIRAL TRIGGER?

Although M.E./PVFS typically follows an infection, usually a viral illness (which may be subsubclinicalal) in a previously fit and active person, it has also been observed to be triggered by other factors such as immunisations, traumas and exposure to chemicals. Furthermore, in a minority of patients, M.E./PVFS has a gradual onset with: no apparent triggering factor. For these reasons proof of a preceding viral illness is not a prerequisite for diagnosis or inclusion in a study group.

ASSESSMENT, INVESTIGATION AND DIAGNOSlS

When diagnosing M.E. for research purposes, particular attention must be paid to two factors:

- many of the symptoms and signs evident in people suffering from M.E./PVFS could be due to a large number of other important diseases/conditions.
- M.E. may run in parallel with other diseases having similar symptoms and signs.

Because it is vital that the M.E. study groups we use in research are as 'pure' as possible, the existence of a parallel disease would be grounds for disqualification. The most common alternative diagnoses/parallel. diseases to be borne in mind before referring a research subject volunteer to an M.E. study group can be considered under the following headings:

Chronic infections:
toxoplasmosis, Lyme disease, HIV infection, chronic active hepatitis, schistosomiasis, brucellosis, occult sepsis, tuberculosis, giardia.

Endocrine disorders:
hypothyroidism, thyrotoxicosis, Addison's disease, Cushing's syndrome, diabetes mellitus, hyperparathyroidism.

Neuromuscular disorders:
myasthenia gravis, multiple sclerosis, mitochondrial myopathy, Parkinson's disease.

Cardiovascular disorders:
cardiac ischaemia.

Metabolic disorders:
sleep apnoea syndrome, chronic renal failure.

Malignant disease:
occult tumours such as undiagnosed lymphomas, retroperitoneal sarcomas; renal and liver tumours; frontal lobe tumours.

Auto-immune disease:
rheumatoid arthritis, systemic lupus erythematosus, thyroiditis, Sjogrens syndrome. Haematological disorders: leukaemias and anaemias of varying origin.

Miscellaneous:
heavy metal poisoning, chronic intoxications due to prolonged exposure to chemicals such as petrol, benzene, organo-phosphorous compounds and methylene chloride; drug side effects such as those due to beta-blockers, and long-term benzodiazepine usage; chronic alcoholism; coeliac disease.

Psychiatric:
primary depressive illness, anxiety neurosis.

OTHER REASONS FOR EXCLUSION FROM RESEARCH INTO M.E.

Of particular importance is to eliminate chronic fatigue primarily associated with psychological factors. If there are signs of persistent anhedonia, apathy, low self-esteem, feelings of worthlessness and guilt, the possibility: of primary depressive illness should be actively considered and, if there is any doubt whatsoever, the subject eliminated from the research study.

If the subject has had any other diseases or conditions in the last three months they should be excluded from, research into M.E.

If the subject has taken any treatments - orthodox, complementary or nutritional - in the last three months they may have to be excluded from certain research projects.

OTHER SYMPTOMS SOMETIMES EXPERIENCED BY PEOPLE WITH M.E./PVFS

Many symptoms are experienced by people suffering from M.E./PVFS and in the right symptomatic context they contribute to the validity of the diagnosis. Nevertheless, not all people suffering from M.E./PVFS experience all these symptoms and their absence does not exclude the condition.

These can be subdivided into the following two categories:

Autonomic
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* bouts of inappropriate night or day-time sweating;
* Raynaud's phenomenon; postural hypotension;
* disturbance of bowel motility manifesting as recurrent diarrhoea or occasionally constipation (these symptoms are frequently indistinguishable from those of irritable bowel syndrome);
* photophobia; blurred vision due to disturbed accommodation;
* hyperacusis;
* frequency of micturition; nocturia.

Immunological (Symptoms suggesting persistent viral infection):
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* episodes of low-grade fever (not exceeding an oral temperature of 38.6C) combined with feeling feverish, (i.e. a down-regulated 'thermostat');
* sore throat which may be persistent or recurrent (i.e. present for at least one week per month);
* arthralgia (fixed or migratory)

This list is by no means exhaustive; headaches, nausea and bloating, for instance, are common symptoms in many patients but are not sufficiently discriminative because of their widespread occurrence in many other disorders. The curious intolerance to alcohol and hypersensitivity to drugs are highly specific in this context. It should also be emphasised that the symptoms of M.E. tend to vary capriciously from hour to hour and day to day. Nevertheless it is absolutely characteristic that they tend to be exacerbated by physical or mental exertion and this association should always be sought whilst taking the history.

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PHYSICAL SIGNS sometomes evident in people suffering from M.E. / PVFS

Characteristic physical signs are seen in M.E./PVFS and in the right symptomatic context they contribute to the validity of the diagnosis. Nevertheless their absence does not exclude the condition, and they are as follows:

(a) Pharyngitis which is either persistent or recurrent (present for at least one week every month) with or without tonsillar enlargement. This is nearly always non-exudative and when present may be accompanied by the low-grade fever mentioned under immunological symptoms.
(b) Tender and possible enlargement of lymph nodes, particularly of the cervical groups; these also may accompany the fever and they may decrease in size during the afebrile periods.
(c) Muscle tenderness with a particular predilection for the neck and shoulder girdle and the major muscles of locomotion. Points of exquisite tenderness are occasionally found by palpating the affected muscles with the tip of a finger.
(d). A positive Romberg test.

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