Investigation of CFS patients is aimed mainly at excluding other illnesses as the cause of fatigue. There are no tests which can be considered to be diagnostic of the condition. Accordingly, there would appear to be no justification for undertaking sophisticated serological investigations nor highly technical radiological investigations in the ordinary course of investigation of the disease unless there are good reasons to suspect a serious occult disease (such as malignancy) as the cause of fatigue.

Medical investigation of patients suspected of having CFS has two main objectives. The first objective is to exclude the existence of other diseases known to cause chronic fatigue. The second objective is to search for evidence of co-existing infections such as the viruses listed above. Since there are no tests to date to corroborate a clinical diagnosis of CFS, investigations should be limited to satisfying these two objectives and need not be extensive unless an individual patient's history justifies it.

Since chronic fatigue syndrome is essentially a diagnosis of exclusion, a comprehensive differential diagnosis schedule is presented here to (a) assist in identifying a range of other serious and life-threatening ataemia, hypoglycaemia, myophosphorylase deficiency and phosphofructokinase deficiency. Muscle pain made worse by exercise is seen in metabolic muscle disorders, in illnesses giving rise to myoglobinuria and in some lipid storage myopathies, particularly in patients with carnitine palmityltransferase deficiency. Many of the metabolic and endocrine conditions listed above are rare.

In some cases, the differential diagnosis needs to be expanded to take account of unusual presenting symptoms in addition to profound fatigue. This is especially so when a patient reports symptoms such as (1) balance disturbances, (2) claudication, (3) gastrointestinal symptoms or (4) fluid retention. The differential diagnosis in the first category should include recurrent, acute and chronic labyrinthitis. In the second category, ischaemia of the cauda equina and occult spinal multiple sclerosis bear consideration.

In the third group, occult gastro-intestinal malignancies need to be excluded. In the fourth category, fluid retention and fatigue are prominent symptoms of the fluid retention syndrome Finally, exclusion of a range of psychiatric ailments is indicated when a patient presents with one or more psychiatric symptoms. The onset of psychiatric illness in CFS is shown to be secondary to the impairment of body function in general and the chronic pain that is part of the condition. There is little, if any, evidence to support a role for any form of psychiatric illness or personality type in the onset of chronic fatigue syndrome.

of the condition is aimed at ensuring an adequate degree of rest in conjunction with a supervised course of gentle graded exercises throughout the course of the illness. Treatment of specific symptoms such as muscle pains and depression are recommended as being appropriate but the use of narcotic and other addictive forms of medication would appear to be inappropriate in all cases. A range of other therapies have been trialed at various times but none have yet to be shown to offer any particular benefit.

Whilst it is not possible to provide specific guidelines to assist in determining the prognosis of individual patients, there is reasonable uniformity of opinion that an improved prognosis is associated with early treatment (including work and lifestyle modifications). Conversely, when the illness is severe or has been present for more than one year or both, the prognosis is generally held to be poorer. Accordingly, early identification of CFS patients is important.

In many cases, temporary removal from the work place is recommended (especially those with severe disease) until there is good evidence of a sustained recovery. For the remainder, it is recommended that placement on lighter duties and/or reduced working hours be initiated early in the course of the illness. Unless the patient has severe disease however, there would appear to be little justification for recommending mandatory removal from the work place if the person is not required to undertake moderate or strenuous duties and if suitable changes to the work environment can be made.