News & Highlights
Chronic Fatigue Syndrome > Healthcare Professionals >
The Revised Case Definition (abridged version)
View Complete Definition
Page Contents
Introduction
The 1988 chronic fatigue syndrome (CFS) working case definition
(Holmes, et al) did not effectively distinguish CFS from other types
of unexplained fatigue. For this reason, it was decided during a 1993
meeting of CFS investigators to develop a logical revision of that
definition. The core of the revised CFS case definition is a set of
uniformly applicable guidelines for the clinical and research
evaluation of CFS and the other forms of fatigue.
In the revised definition, a consensus viewpoint from many of the
leading CFS researchers and clinicians (including input from patient
group representatives), chronic fatigue syndrome is treated as a
subset of chronic fatigue, a broader category defined as unexplained
fatigue of greater than or equal to six month's duration. Chronic
fatigue in turn, is treated as a subset of prolonged fatigue, which is
defined as fatigue lasting one or more months. The expectation is that
scientists will devise epidemiologic studies of populations with
prolonged fatigue and chronic fatigue, and search within those
populations for illness patterns consistent with CFS.
Guidelines for the Evaluation and Study of CFS
A thorough medical history, physical examination, mental status
examination, and laboratory tests (diagram) 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:
-
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.
-
The concurrent occurrence of four or more of the following
symptoms: substantial impairment in short-term memory or
concentration; sore throat; tender lymph nodes; muscle pain;
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
-
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.
-
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 infection.
-
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
-
anorexia nervosa
-
or bulemia nervosa
-
Alcohol or other substance abuse, occurring within 2 years of the
onset of chronic fatigue and any time afterwards.
-
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
-
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.
-
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.
-
Any condition, such as Lyme disease or syphillis, that was treated
with definitive therapy before development of chronic symptoms.
-
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. 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
tomography).
Page last modified on May 5, 2006