Chapter Two, Course WB1032
CFS Evaluation and Diagnosis Model
Given the complexity of CFS, how can primary health care professionals diagnose the presence of chronic fatigue syndrome with a greater degree of confidence?
In the development phase of this curriculum, clinicians Drs. Nancy Klimas and Charles Lapp created a decision-making model from the case definition to guide clinical assessment of patients with CFS-like symptoms. This model provides a step-wise approach to making a sound clinical diagnosis.
The physical exam will focus on ruling out alternative diagnoses. Clinical evaluation of people with a fatiguing illness requires: 1) a detailed patient history, including review of medications that could cause fatigue; 2) a thorough physical examination; 3) a mental status screening; and 4) a minimum battery of laboratory screening tests.
Recommended lab tests include:
- Urinalysis
- Complete blood count (CBC) with leukocyte differential
- Erythrocyte sedimentation rate (ESR)
- Total protein
- C-reactive protein
- Alanine aminotransferase (ALT) or aspartate transaminase serum level (AST)
- Alkaline phosphatase (ALP)
- Blood urea nitrogen (BUN)
- Electrolytes
- Creatinine
- Albumin
- Globulin
- Glucose
- Calcium
- Phosphorus
- Thyroid function tests (TSH and Free T4)
- ANA and rheumatoid factor
Routinely doing other laboratory tests for all patients with chronically fatiguing illnesses has limited value. For example, it is inappropriate to test initially for antibodies to EBV in all people with CFS symptoms, even though EBV can be associated with a prolonged infection that has all the features of CFS. Diagnosis requires a complete clinical evaluation and cannot be accomplished by merely testing for antibodies. Since 95% of adults have been infected with EBV, most adults will show antibodies to EBV from infection incurred years earlier. High or elevated antibody levels may be present for years and are not diagnostic of recent infection. Studies have shown that EBV antibodies can be present in 20% of healthy individuals for years (U.S. Centers for Disease Control and Prevention, 2002, Summary of Interpretation, paragraph 3).
Further tests may be indicated to confirm or exclude other diagnoses, which better explain the persistent fatigue state (e.g., polysomnography for a patient with suspected sleep apnea or a multiple sleep latency test for narcolepsy).
A mental state examination of individuals with fatigue should focus on observed behavioral features in addition to symptoms reported by the patient. These include psychomotor slowing, cognitive impairment, odd interpersonal behavior and angry/hostile responses. In addition, it is important to evaluate the individual’s risk of suicide.
Although CFS requires fatigue of at least six months duration, initial evaluation of patients with fatigue should not focus on fatigue as a distinct entity. Rather, the entire presenting symptom complex must be evaluated. If the patient has had symptoms of chronic fatigue for less than six months, then he/she needs to be re-evaluated depending on the results of the physical evaluation. Also, it is important to remember that six months is not a magic number. One should not wait until fatigue has been present for six months or longer to consider the patient’s complaints. Appropriate evaluation and therapy need to be initiated early.
If the fatigue is chronic/relapsing for six or more consecutive months and is unrelieved by bed rest, then determine if the fatigue has significantly affected the patient’s lifestyle, ability to work or attend school.
If no other plausible explanations are found for the fatiguing illness, then assess the patient to see if he or she meets four or more of the eight CFS symptom criteria. However, the primary health care professional should exercise judgment here, based on the course of illness, other symptomology and the patient’s medical history. Fewer than four of the eight symptom criteria may be diagnostic for a non-syndromic chronic fatigue.
If the patient has had more than six months of fatigue and indicates that it has not had a major affect on his/her lifestyle or work then the patient should be diagnosed with non-syndromic chronic fatigue. Conservative treatment with periodic follow-up is appropriate.
CFS is excluded if another plausible explanation is found. Confounding conditions need to be treated and the patient needs to be re-evaluated regularly.
If all diagnostic criteria are met, and other plausible conditions have been ruled out, the diagnosis of CFS can be made.
Content Source: National Center for Zoonotic, Vector-Borne, and Enteric Diseases (ZVED)