Diagnosis of Chronic Fatigue Syndrome

If a patient has had six or more consecutive months of severe fatigue that is reported to be unrelieved by sufficient bed rest and that is accompanied by nonspecific symptoms, including flu-like symptoms, generalized pain, and memory problems, the physician should further investigate the possibility that the patient may have CFS.

How Physicians Diagnose CFS

 The first step in the investigation is obtaining a detailed medical history and performing a complete physical examination of the patient. Initial testing should include a mental status examination, which ordinarily will involve a short discussion in the office or a brief oral test. A standard series of laboratory tests of the patient's blood and urine should be performed to help the physician identify other possible causes of illness. If test results suggest an alternative explanation for the patient's symptoms, additional tests may be performed to confirm that possibility. If no cause for the symptoms is identified, the physician may render a diagnosis of CFS if the other conditions of the case definition are met (see What Is CFS?, part a). A diagnosis of idiopathic chronic fatigue could be made if a patient has been fatigued for 6 months or more, but does not meet the symptom criteria for CFS.

While the number and type of tests performed may vary from physician to physician, the following tests constitute a typical standard battery to exclude other causes of fatiguing illness: alanine aminotransferase (ALT), albumin, alkaline phosphatase (ALP), blood urea nitrogen (BUN), calcium, complete blood count, creatinine, electrolytes, erythrocyte sedimentation rate (ESR), globulin, glucose, phosphorus, thyroid stimulating hormone (TSH), total protein, transferrin saturation, and urinalysis. Further testing may be required to confirm a diagnosis for illness other than CFS. For example, if a patient has low levels of serum albumin together with an above-normal result for the blood urea nitrogen test, kidney disease would be suspected. The physician may choose to repeat the relevant tests and possibly add new ones aimed specifically at diagnosing kidney disease. If autoimmune disease is suspected on the basis of initial testing and physical examination, the physician may request additional tests, such as for antinuclear antibodies.

Psychological/Neuropsychological Testing

In some individuals it may be beneficial to assess the impact of fatiguing illness on certain cognitive or reasoning skills, e.g., concentration, memory, and organization. This may be particularly relevant in children and adolescents, where academic attendance, performance, and specific educational needs should be addressed. Personality assessment may assist in determining coping abilities and whether there is a co-existing affective disorder requiring treatment.

A number of tests, some of which are offered commercially, have no demonstrated value for the diagnosis of CFS. These tests should not be performed unless required for diagnosis of a suspected exclusionary condition (e.g., MRI to rule out suspected multiple sclerosis) or unless they are part of a scientific study. In the latter case, written informed consent of the patient is required. No diagnostic tests for infectious agents, such as Epstein-Barr virus, enteroviruses, retroviruses, human herpesvirus 6, Candida albicans, and Mycoplasma incognita, are diagnostic for CFS and as such should not be used (except to identify an illness that would exclude a CFS diagnosis, such as mononucleosis). In addition, no immunologic tests, including cell profiling tests such as measurements of natural killer cell (NK) number or function, cytokine tests (e.g., interleukin-1, interleukin-6, or interferon), or cell marker tests (e.g., CD25 or CD16), have ever been shown to have value for diagnosing CFS. Other tests that must be regarded as experimental for making the diagnosis of CFS include the tilt table test for NMH, and imaging techniques such as MRI, PET-scan, or SPECT-scan. Reports of a pathway marker for CFS as well as a urine marker for CFS are undergoing further study; however, neither is considered useful for diagnosis at this time.