According to the CDC, the diagnosis of CFS is based on the patient (1) having severe chronic fatigue of at least 6 months' duration, with other known medical conditions excluded by clinical diagnosis, and (2) concurrently having four or more of the following symptoms:

• Substantial impairment in short-term memory or concentration

• Sore throat

• Tender lymph nodes

• Muscle pain

• Multijoint pain without swelling or redness

• Headaches of a new type, pattern or severity

• Unrefreshing sleep

• Postexertional malaise lasting more than 24 hours

The symptoms must have persisted or recurred during 6 or more consecutive months of illness and must not have predated the fatigue.

For more on the diagnostic criteria for CFS, read here.

Some have suggested that the infectious agent responsible for CFS is Chlamydia pneumoniae, which may become activated after contact with another infectious agent. In hospitals or commercial laboratories, immunoglobulin M (IgM) tests and immunoglobulin G (IgG) enzyme-linked immunosorbent assay are used to test for antibodies against C pneumoniae. As with elevated Epstein-Barr virus IgG viral capsid antigen titers, many individuals in the healthy population have elevated IgG titers to C pneumoniae, making the epidemiologic link to CFS more difficult.

Some patients with CFS are found to have elevated IgM C pneumoniae titers, indicating a recent C pneumoniae infection, and these patients are the most likely to respond to antichlamydial therapy. However, definitive proof supporting causality is lacking.

For more on the etiology of CFS, read here.

CFS should be diagnosed only after other causes of fatigue are excluded and the fatigue has lasted for at least 6 months. An absence of cognitive difficulties should exclude a diagnosis of CFS. Signs of adrenal or thyroid disorders should also exclude a diagnosis of CFS, in that the fatigue is explained by endocrinologic factors. Similarly, HIV infection and AIDS may also cause chronic fatigue.

In most patients, the physical examination is unrevealing. However, many patients have small, moveable, painless lymph nodes that most commonly involve the neck, axillary region, or inguinal region. A single lymph node that is very large, tender, or immobile suggests a diagnosis other than CFS. Similarly, generalized adenopathy suggests a diagnosis other than CFS.

An isolated report from a single center suggested that a purple or crimson discoloration of both anterior tonsillar pillars (crimson crescents) in the absence of pharyngitis is might be a marker in patients with CFS. The cause of crimson crescents is unknown, but they are common in patients with CFS. However, crimson crescents are not specific for CFS, and additional studies are needed to determine the true frequency of this finding in patients with CFS.

Trigger points, which suggest fibromyalgia, are absent in patients with CFS. CFS and fibromyalgia rarely coexist in the same patient.

For more on the physical examination of CFS, read here.

The most consistent laboratory abnormality in patients with CFS is an extremely low ESR, typically in the range of 0-3 mm/h. A normal ESR or one that is in the upper reference range suggests another diagnosis. Most patients with CFS usually have two or three of the following nonspecific abnormalities:

• Elevated IgM/ IgG coxsackievirus B titer

• Elevated IgM/IgG human herpesvirus 6 titer

• Elevated IgM/IgG C pneumoniae titer

• Decrease in natural killer cells (either percentage or activity)

The white blood cell count in patients with CFS is normal. Leukopenia, leukocytosis, or an abnormal cell differential count indicates a diagnosis other than CFS, and another cause should be pursued to explain these findings.

Results of liver function tests are within the reference range in patients with CFS. Increased levels of serum aminotransferases, alkaline phosphatase, or lactic dehydrogenase should prompt a search for another explanation because these values are typically normal in CFS. Serum protein electrophoresis is normal in patients with CFS but may be used to rule out other diseases that cause fatigue, including lymphoma and myeloma. Urinalysis findings are unremarkable in CFS.

For more on the workup of CFS, read here.

Because most cases of CFS may be due to a viral infection, no uniformly effective therapy exists for CFS. Trials of antiviral agents have been ineffective in relieving the symptoms of CFS. In patients with elevated C pneumoniae levels, particularly those with increased IgM titers, antichlamydial therapy may be effective. No special diet or vitamin supplements are effective. Otherwise, treatment is largely supportive and responsive to symptoms.

For more the treatment of CFS, read here.

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Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.

Cite this article: Michael Stuart Bronze. Quiz: How Much Do You Know About Chronic Fatigue Syndrome? Medscape. Dec 04, 2015.