Methods for identifying chronic fatigue syndrome

No test is currently available that can identify chronic fatigue syndrome (also known as myalgic encephalomyelitis). The diagnosis is guided by criteria established in 2015 that include common features of the condition and exclusion of other explanations for the findings.

The criteria require these 3 symptoms:

• New onset of fatigue that is not improved with rest causing a marked decrease in ability to perform normal activities for at least 6 months without clear explanation

• Fatigue that is made worse by physical exertion or cognitive stress that previously did not cause problems.

• Feeling unrested despite adequate sleep

In addition, at least one of the following two symptoms are required:

• Problems with brain function (such as concentrating or planning ahead) that is made worse by stress or exertion

• Worsened symptoms when upright and improved by lying down or elevating the feet

Routine tests are recommended to rule out other common explanations for these symptoms. Such tests include:

• Blood counts

• Standard chemistry tests (such as electrolytes and tests of kidney and liver function)

• Testing of thyroid function

• Other testing based on symptoms – For example, if muscle pain or weakness are present, muscle enzyme tests should be checked.