How Chronic Fatigue Syndrome Is Diagnosed

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CFS diagnosis
© Verywell, 2018 

The path to a diagnosis of chronic fatigue syndrome (CFS) can be frustrating. The condition is characterized by its symptoms and there is no single test that can confirm it. Complicating the issue even further is the fact that many CFS symptoms mirror those of other illnesses, including heart, lung, thyroid, and even psychiatric disorders. As a disease, chronic fatigue syndrome is diagnosed when other possible explanations for how you are feeling have been explored and excluded. The condition is also called myalgic encephalomyelitis (ME/CFS) or systemic exertion intolerance disease (SEID).

Self-Checks

You can't diagnose yourself with chronic fatigue syndrome, but you can (and are encouraged to) heighten your awareness of your symptoms, their frequency, and possible triggers. This information will greatly help your doctor with the diagnostic process.

Start by getting to know the range of possible chronic fatigue symptoms; you may be experiencing some you might otherwise not think are worth raising to your doctor. Then, consider keeping a symptom diary, which may help you find patterns of things things that make you feel better or worse. Also, think back to an episode of illness or stress that occurred soon before you began to experience the symptoms for the first time and take note of it.

You can further prepare for a visit with your doctor by writing down answers to these likely questions:

  • How long have you had these symptoms?
  • How do the things you are able to do now differ from what you were able to do before you began to have these symptoms? Do your symptoms prevent you from doing certain activities?
  • How do you feel if you try to do activities that now feel difficult?
  • What specific activities make you feel worse?
  • Does sleeping or resting help you feel better? 
  • Do you have any sleep problems?
  • What helps you the most when you feel fatigued?
  • Do you have any problems thinking clearly?

Evaluation

Your doctor will use all of this information to come to a diagnosis. In fact, even though he or she will perform tests as part of this process, the history of your symptoms will be the most significant data your doctor will need for determining whether you have ME/CFS. 

In 2015, the National Academy of Medicine (NAM, formerly the Institute of Medicine) defined the chief symptoms that indicate the condition. A person may be diagnosed with ME/CFS if they meet all of the following criteria:

  • Six months of profound, unexplained fatigue
  • Post-exertional malaise for more than 24 hours after mental or physical exertion: This means that you have fatigue and worsening of other symptoms, which can continue for days.
  • Unrefreshing sleep: You wake up tired, even with ample sleep. You may also have other sleep disturbances such as insomnia or an inability to stay asleep.
  • Either cognitive problems (brain fog) or orthostatic intolerance (dizziness upon standing due to blood pressure irregularities)

There are many other symptoms frequently experienced by people with ME/CFS, including muscle or joint pain, headaches, sore throat, enlarged lymph nodes in the neck or armpits, and a feeling of generally being sick.

Your doctor will complete a full physical examination as part of his or her evaluation as well.

Labs and Tests

Laboratory tests will not show any unusual results if you have ME/CFS but may show that you have other conditions that are producing your symptoms (either entirely or in part).

The laboratory tests you may expect include complete blood count (CBC), glucose, calcium, electrolytes, BUN, creatinine, erythrocyte sedimentation rate (ESR), and thyroid stimulating hormone (TSH). These are general screens for anemia, infection, kidney function, liver function, inflammation, and thyroid disease.

Your doctor may assess your fatigue, cognitive impairment, and other symptoms with tools or questionnaires such as the CDC Symptom Inventory for CFS, Sleep Assessment Questionnaire, Wood Mental Fatigue Inventory, and PROMIS pain assessment tool.

You are likely to have more extensive tests if your physical examination or symptoms point to other conditions. For example, you might have tests for antinuclear antibodies if systemic lupus erythematosus is suspected, thyroid function tests if you could have hypothyroidism, sleep studies, or tests for adrenal insufficiency. You might be referred to a neurologist, rheumatologist, or sleep specialist for assessment.

Imaging such as a chest X-ray, MRI, or CT scan is only done if other findings indicate a condition such as heart disease, lung disease, cancer, or multiple sclerosis.

Again, remember that one of these or other issues, and not chronic fatigue syndrome, could alone be the cause of your symptoms, or it could be affecting you ​in addition to ME/CFS.

Differential Diagnoses

To tease this all out, diagnosis of CFS is made by exclusion, meaning that a doctor will explore other conditions that may cause fatigue, body aches, swollen lymph nodes, and cognitive impairment.

The list is potentially exhaustive, and the process can be lengthy and sometimes tedious. The evaluation may involve tests for the following conditions:

Even if a positive diagnosis of depression is made, it doesn't necessarily rule out CFS since depression is an almost inextricable symptom of long-term fatigue. As such, the diagnosis needs to be made by a doctor experienced in CFS who is better able to differentiate these conditions.

View Article Sources
  • Beyond Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Redefining an Illness. Washington: The National Academies Press; 2015.
  • Centers for Disease Control and Prevention. Diagnosis. https://www.cdc.gov/me-cfs/symptoms-diagnosis/diagnosis.html.
  • Gluckman, S. Chronic Fatigue Syndrome. Merck Manual Professional Version. https://www.merckmanuals.com/professional/special-subjects/chronic-fatigue-syndrome/chronic-fatigue-syndrome.