The CDC (Fukuda 1994) Definition for Chronic Fatigue Syndrome
Guidelines for the Evaluation and Study of CFS:
A thorough medical history, physical examination, mental status examination, and laboratory tests
must be conducted to identify underlying or contributing conditions that require treatment. Diagnosis or
classification cannot be made without such an evaluation. Clinically evaluated, unexplained chronic fatigue
cases can be classified as chronic fatigue syndrome if the patient meets both the following criteria:
1. Clinically evaluated, unexplained persistent or relapsing chronic fatigue that is of new or definite onset
(i.e., not lifelong), is not the result of ongoing exertion, is not substantially alleviated by rest, and results
in substantial reducation in previous levels of occupational, educational, social, or personal activities.
2. The concurrent occurrence of four or more of the following symptoms:
substantial impairment in short-term memory or concentration;
tender lymph nodes;
multi-joint pain without swelling or redness;
headaches of a new type, pattern, or severity;
unrefreshing sleep; and
post-exertional malaise lasting more than 24 hours.
These symptoms must have persisted or recurred during 6 or more consecutive months of illness and must not have
predated the fatigue.
Conditions that Exclude a Diagnosis of CFS
1. Any active medical condition that may explain the presence of chronic fatigue, such as
untreated hypothyroidism, sleep apnea and narcolepsy, and iatrogenic conditions such as side
effects of medication.
2. Some diagnosable illnesses may relapse or may not have completely resolved during treatment.
If the persistence of such a condition could explain the presence of chronic fatigue, and if it
cannot be clearly established that the original condition has completely resolved with treatment,
then such patients should not be classified as having CFS. Examples of illnesses that can present
such a picture include some types of malignancies and chronic cases of hepatitis B or C virus
3. Any past or current diagnosis of a major depressive disorder with psychotic or melancholic features;
bipolar affective disorders
schizophrenia of any subtype
delusional disorders of any subtype
dementias of any subtype
or bulemia nervosa
4. Alcohol or other substance abuse, occurring within 2 years of the onset of chronic fatigue and any time
5. Severe obesity as defined by a body mass index [body mass index = weight in kilograms ÷ (height in meters)2]
equal to or greater than 45. [Note: body mass index values vary considerably among different age groups and
populations. No "normal" or "average" range of values can be suggested in a fashion that is meaningful. The
range of 45 or greater was selected because it clearly falls within the range of severe obesity.]
Any unexplained abnormality detected on examination or other testing that strongly suggests an exclusionary
condition must be resolved before attempting further classification.
Conditions that do not Exclude a Diagnosis of CFS
1. Any condition defined primarily by symptoms that cannot be confirmed by diagnostic laboratory tests, including
fibromyalgia, anxiety disorders, somatoform disorders, nonpsychotic or melancholic depression, neurasthenia, and
multiple chemical sensitivity disorder.
2. Any condition under specific treatment sufficient to alleviate all symptoms related to that condition and for
which the adequacy of treatment has been documented. Such conditions include hypothyroidism for which the adequacy
of replacement hormone has been verified by normal thyroid-stimulating hormone levels, or asthma in which the
adequacy of treatment has been determined by pulmonary function and other testing.
3. Any condition, such as Lyme disease or syphillis, that was treated with definitive therapy before development
of chronic symptoms.
4. Any isolated and unexplained physical examination finding, or laboratory or imaging test abnormality that is
insufficient to strongly suggest the existence of an exclusionary condition. Such conditions include an elevated
antinuclear antibody titer that is inadequate, without additional laboratory or clinical evidence, to strongly
support a diagnosis of a discrete connective tissue disorder.
A Note on the Use of Laboratory Tests in the Diagnosis of CFS
A minimum battery of laboratory screening tests should be performed. Routinely performing other screening tests
for all patients has no known value. However, further tests may be indicated on an individual basis to confirm or
exclude another diagnosis, such as multiple sclerosis. In these cases, additional tests should be done according
to accepted clinical standards.
The use of tests to diagnose CFS (as opposed to excluding other diagnostic possibilities) should be done only in
the setting of protocol-based research. The fact that such tests are investigational and do not aid in diagnosis
or management should be explained to the patient.
In clinical practice, no tests can be recommended for the specific purpose of diagnosing chronic fatigue
syndrome. [Emphasis added.]
Tests should be directed toward confirming or excluding other possible clinical conditions. Examples of specific
tests that do not confirm or exclude the diagnosis of chronic fatigue syndrome include serologic tests for
Epstein-Barr virus, enteroviruses, retroviruses, human herpesvirus 6, and Candida albicans; tests of immunologic
function, including cell population and function studies; and imaging studies, including magnetic resonance
imaging scans and radionuclide scans (such as single-photon emission computed tomography and positron emission
From "The Chronic Fatigue Syndrome: A Comprehensive Approach to its Definition and Study".
Keiji Fukuda, M.D., M.P.H., Stephen E. Straus, M.D., Ian Hickie, M.D., F.R.A.N.Z.C.P., Michael C. Sharpe,
M.R.C.P., M.R.C. Psych., James G. Dobbins, Ph.D., Anthony L. Komaroff, M.D., F.A.C.P. and the International
Chronic Fatigue Syndrome Study Group. Annals of Internal Medicine, Vol. 121, December 15, 1994, pp. 953-959.