Q: How is chronic fatigue syndrome diagnosed?

A: Chronic fatigue syndrome (CFS), also known as myalgic encephalomyelitis or chronic fatigue and immune dysfunction syndrome, is diagnosed by excluding known medical and psychiatric illnesses that also exhibit fatigue and similar symptoms. It is important to diagnose these conditions because treatments may be available. Some diseases eliminate a diagnosis of CFS, such as multiple sclerosis, lupus or a severe psychiatric disorder such as schizophrenia. It would not provide any benefits in these cases to have a second diagnosis.

Diseases that also have fatigue include: hypothyroidism, sleep apnea, narcolepsy, alcohol or substance abuse, severe obesity, lupus, multiple sclerosis, cancer, depression, anorexia nervosa, bulimia nervosa, schizophrenia, bipolar disorder and dementia.

The current diagnostic criteria for CFS specify unexplained, persistent fatigue that's not due to ongoing exertion, isn't substantially relieved by rest, started recently and leads to significant reduction in previous activity levels. They also require the presence of at least four of the following symptoms: unrefreshing sleep, impairment in short-term memory or concentration, post-exertional malaise occurring within 12 to 24 hours of exertion and lasting 24 hours or more, joint pain without joint swelling or redness, muscle discomfort or pain, headaches of a new type or severity, recurrent sore throat and tender lymph nodes in the neck and underarms.

Multiple subjective symptoms are also reported. These are not included in the current diagnostic criteria, but they are reported with relative frequency. These include: irritable bowel syndrome and other gastrointestinal complaints, allergy-like symptoms, skin rashes, visual disturbances, dizziness, numbness and tingling in arms and legs, sensitivities to various chemicals, dry eyes, chills, night sweats and alcohol and medication intolerances.

Some CFS patients also report mild to moderate symptoms of anxiety or depression. However, many people with CFS don't have depression or any other psychiatric illness. Depression may be a secondary effect of CFS, not necessarily a primary condition, as people attempt to cope with the changes in lifestyle that living with a chronic illness dictates. Still, if you are anxious or depressed, it's essential to get help.

Allergies also tend to be more common in CFS patients than in the general population. Many CFS patients have a history of allergies years before the onset of the syndrome. Sometimes patients report a worsening of allergic symptoms or the onset of new allergies after becoming ill with CFS. Because allergies are so common in people with CFS, it is important to identify symptoms caused by allergies so they can be treated independently.

Your health care professional should take a thorough medical history and conduct extensive physical and mental status examinations, including laboratory tests.