Diagnosis

A definitive diagnosis of fatigue is difficult to make. The objective is to identify any underlying physical, psychosocial or physiological factors which may be the source of tiredness.

• medications and toxic exposures
  • long-acting antihistamines, corticosteroids, neuroleptics, antiarrhythmics (e.g., amiodarone), antidepressants and antihypertensives (e.g., clonidine, alpha methyldopa and beta-blockers) and some herbal remedies
  • environmental toxins - carbon monoxide, lead, mercury and arsenic (1)
    
    
• history
  • fatigue's duration (recent, prolonged or chronic), onset (sudden or progressive), recovery period (short or long)
  • patients physical activity (sedentary or active) (1)
  • aggravating and relieving factors (2)
  • particular useful in differentiating chronic fatigue from chronic fatigue syndrome (CFS) - CFS presents with sudden onset with recovery occurring in hours or days
  • psychiatric assessment
    • fatigue is the chief complaint in most of the psychiatric disorders (3)
    • should enquire about depression, stress, anxiety, eating disorders, somatisation disorder (2,3)
    • substance abuse (caffeine, alcohol and illicit drugs)
  • assessment for sleep disorder
    • sleep apnoea, excessive sleepiness and parasomnias (1)
      
      
• physical examination
  • to identify any organ based diseases e.g - breathlessness, weight loss, anorexia (2)

The following can be used as first line investigations in primary care to rule out any serious and common underlying diseases:

• FBC
• ESR
• thyroid stimulating hormone
• fasting blood glucose level
• additional possible investigations include:
  • liver function test
  • serum urea, electrolyte and creatinine levels
  • serum ferritin (indicated as an initial investigation in children and young adults only)
  • urinalysis for protein, blood and glucose
  • blood test for gluten sensitivity
  • serum calcium (1,2)

Reference:

• 1. Cornuz J. Fatigue: a practical approach to diagnosis in primary care. CMAJ 2006;174(6)
• 2. Simon C. Tiredness, fatigue and lethargy. InnovAiT 2008 1(3):199-205
• 3. Wilks D, Sharpe M. Fatigue. BMJ. 2002 August 31; 325(7362): 480-483
• 4. BPAC NZ 2006. The laboratory investigation of tiredness