ME International:

Chronic Fatigue Syndrome
Definition, Symptoms, Diagnosis

Below is the CDC's current position on CFS for Healthcare Professionals. This revised case definition is the 1994 Fukuda et al, definition (rebranding ?). As the CDC's defining symptom is prolonged fatigue, the definition and diagnostic symptoms are the same. Although, "A number of illnesses have been described that have a similar spectrum of symptoms to CFS. These include fibromyalgia syndrome, myalgic encephalomyelitis, neurasthenia, multiple chemical sensitivities, and chronic mononucleosis. Although these illnesses may present with a primary symptom other than fatigue, chronic fatigue is commonly associated with all of them." these illnesses are not CFS.

The Revised Case Definition from the (abridged version) Reeves et al (2003)

View 1994 Fukuda et al Definition

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

For use as research inclusion critera ?

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; 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

  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 infection.
  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
    • anorexia nervosa
    • or bulemia nervosa
  4. Alcohol or other substance abuse, occurring within 2 years of the onset of chronic fatigue and any time afterwards.
  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.( note myalgic encephalomyelitis is not there, if you have ME you can not have CFS? )
  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.('before development of chronic symptoms' as if chronic Lyme does not have chronic symptoms? not to mention syphillis )
  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 bly support a diagnosis of a discrete connective tissue disorder.


For use in the clinical setting ?

Chronic fatigue syndrome shares symptoms with many other disorders. Fatigue, for instance, is found in hundreds of illnesses, and 10% to 25% of all patients who visit general practitioners complain of prolonged fatigue. The nature of the symptoms, however, can help clinicians differentiate CFS from other illnesses.

Primary Symptoms

As the name chronic fatigue syndrome suggests, this illness is accompanied by fatigue. However, it's not the kind of fatigue patients experience after a particularly busy day or week, after a sleepless night or after a stressful event. It's a severe, incapacitating fatigue that isn't improved by bed rest and that may be exacerbated by physical or mental activity. It's an all-encompassing fatigue that results in a dramatic decline in both activity level and stamina.

People with CFS function at a significantly lower level of activity than they were capable of prior to becoming ill. The illness results in a substantial reduction in occupational, personal, social or educational activities.

A CFS diagnosis should be considered in patients who present with six months or more of unexplained fatigue accompanied by other characteristic symptoms. These symptoms include:

  • cognitive dysfunction, including impaired memory or concentration
  • postexertional malaise lasting more than 24 hours (exhaustion and increased symptoms) following physical or mental exercise
  • unrefreshing sleep
  • joint pain (without redness or swelling)
  • persistent muscle pain
  • headaches of a new type or severity
  • tender cervical or axillary lymph nodes
  • sore throat

Other Common Symptoms

In addition to the eight primary defining symptoms of CFS, a number of other symptoms have been reported by some CFS patients. The frequency of occurrence of these symptoms varies among patients. These symptoms include:

  • irritable bowel, abdominal pain, nausea, diarrhea or bloating
  • chills and night sweats
  • brain fog
  • chest pain
  • shortness of breath
  • chronic cough
  • visual disturbances (blurring, sensitivity to light, eye pain or dry eyes)
  • allergies or sensitivities to foods, alcohol, odors, chemicals, medications or noise
  • difficulty maintaining upright position (orthostatic instability, irregular heartbeat, dizziness, balance problems or fainting)
  • psychological problems (depression, irritability, mood swings, anxiety, panic attacks)
  • jaw pain
  • weight loss or gain

Clinicians will need to consider whether such symptoms relate to a comorbid or an exclusionary condition; they should not be considered as part of CFS other than they can contribute to impaired functioning.

Clinical Course

The severity of CFS varies from patient to patient, with some people able to maintain fairly active lives. By definiton, however, CFS significantly limits work, school and family activities.

While symptoms vary from person to person in number, type and severity, all CFS patients are functionally impaired to some degree. CDC studies show that CFS can be as disabling as multiple sclerosis, lupus, rheumatoid arthritis, heart disease, end-stage renal disease, chronic obstructive pulmonary disease (COPD) and similar chronic conditions.

CFS often follows a cyclical course, alternating between periods of illness and relative well-being. Some patients experience partial or complete remission of symptoms during the course of the illness, but symptoms often reoccur. This pattern of remission and relapse makes CFS especially hard for patients and their health care professionals to manage. Patients who are in remission may be tempted to overdo activities when they're feeling better, which can exacerbate symptoms and fatigue and cause a relapse. In fact, postexertional malaise is a hallmark of the illness.

The percentage of CFS patients who recover is unknown, but there is some evidence to indicate that the sooner symptom management begins, the better the chance of a positive therapeutic outcome. This means early detection and treatment are of utmost importance. CDC research indicates that delays in diagnosis and treatment may complicate and prolong the clinical course of the illness.


Diagnostic Challenges

Diagnosing chronic fatigue syndrome (CFS) can be challenging for health care professionals. A number of factors add to the complexity of making a CFS diagnosis: 1) there's no diagnostic laboratory test or biomarker for CFS, 2) fatigue and other symptoms of CFS are common to many illnesses, 3) CFS is an invisible illness and many patients don't look sick, 4) the illness has a remitting and relapsing course , 5) symptoms vary from person to person in frequency and severity, and 6) no two CFS patients have exactly the same pattern of symptoms.

These factors have contributed to an alarmingly low diagnosis rate. Of the four million Americans who have CFS, less than 20% have been diagnosed.

One has to wonder about the suffering and fate of that other 80%

Overcoming the Challenges

In spite of these challenges, CFS can be diagnosed in a primary care setting. The 1994 International Case Definition for CFS forms the basis of a reliable diagnostic algorithm for CFS, particularly in adults.

While there is evidence that children can get CFS, current research suggests that the illness isn't prevalent in younger children, particularly those under the age of 11. Diagnosing pediatric CFS can be more difficult than adult CFS because children may have difficulty recognizing and verbalizing their symptoms, and because they have a remarkable ability to become accustomed to symptoms and adapt to them. Clinicians assessing adolescents for CFS should exercise judgment based on the course of the illness and the patient's medical history.( long term adult sufferers after time and acceptance of cfs also 'have a remarkable ability to become accustomed to symptoms and adapt to them'

How Physicians Diagnose CFS

If a patient has had 6 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. The first step in this 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 ( should be, have to 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. A diagnosis of insufficient fatigue (ISF) could be made if a patient has been fatigued for 6 months or more, but does not meet the symptom criteria for CFS.

An Empirical Definition

Recently the definitional criteria have reached using information derived from 3 questionnaires: MOS SF-36, Multidimensional Fatigue Inventory, and the CDC Symptom Inventory (Reeves et al, 2005). This approach can be useful in identifying patient and in monitoring their illness course or response to treatment.
( Chronic Fatigue Syndrome – A clinically empirical approach to its definition and study.  
William C Reeves, Dieter Wagner, Rosane Nisenbaum, James F Jones, Brian Gurbaxani, Laura Solomon1, Dimitris A Papanicolaou, Elizabeth R Unger, Suzanne D Vernon and Christine Heim (2005) )

Appropriate Tests for Routine Diagnosis of 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.

A Note on the Use of Laboratory Tests in the Diagnosis of CFS

This section 'Use of Laboratory Tests' is part of 'Guidelines for the Evaluation and Study of CFS', including it here is of more value to people seeking answers.

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).

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.

This is also relevant for all newly diagnosed patients as it gives a base line for future reference. For those who enter the long term category, your status quo can become the recent past thus your functioning levels when you first became ill are not clearly recalled( not to mention pre-illness). Without these base levels you have no way of judging your progress.

Chronic Fatigue Syndrome – A clinically empirical approach to its definition and study. William C Reeves, Dieter Wagner, Rosane Nisenbaum, James F Jones, Brian Gurbaxani, Laura Solomon1, Dimitris A Papanicolaou, Elizabeth R Unger, Suzanne D Vernon and Christine Heim (2005)

    Now review the ME/CFS Clinical Working Case Definition, Diagnostic and Treatment Protocols Carruthers et al., 2003, for a more clinical and diagnosistic perspective on ME / CFS.

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