What tests should be ordered for a patient with fatigue?

Diagnostic Testing for Fatigue

For patients presenting with fatigue, a comprehensive laboratory evaluation should include complete blood count, comprehensive metabolic panel, thyroid function tests, inflammatory markers, iron studies, vitamin D level, and urinalysis. 1

Initial Assessment

When a patient presents with fatigue, the first step is to quantify its severity using a validated scale:

• Use the Numeric Rating Scale (0-10) for initial screening:

  • 0-3: Mild fatigue
  • 4-6: Moderate fatigue
  • 7-10: Severe fatigue 2, 1

• For moderate to severe fatigue (score ≥4), proceed with comprehensive assessment 2

Laboratory Evaluation

Essential Laboratory Tests:

1. Complete Blood Count (CBC)

   • Evaluates for anemia, infection, or inflammation 1

2. Comprehensive Metabolic Panel (CMP)

   • Assesses electrolyte imbalances, kidney and liver function 1

3. Thyroid Function Tests

   • TSH and free T4 to evaluate thyroid dysfunction 2, 1

4. Inflammatory Markers

   • ESR and C-reactive protein (CRP) 2, 1

5. Iron Studies

   • Serum iron, ferritin, TIBC, and transferrin saturation 1

6. Urinalysis

   • Evaluates for protein, blood, glucose, and infection 2

Additional Tests Based on Clinical Suspicion:

1. Vitamin D Level

   • Particularly in patients with malabsorption conditions 1

2. Fasting Blood Glucose/HbA1c

   • To evaluate for diabetes 1

3. Cortisol Levels

   • To evaluate for adrenal insufficiency 1

4. Sex Hormone Levels

   • To evaluate for hypogonadism 1

5. BNP or NT-proBNP

   • To evaluate for heart failure 1

6. Autoimmune Markers

   • When rheumatologic disease is suspected 1

Physical Examination Focus Areas

The physical examination should specifically assess:

• Vital signs, including orthostatic measurements
• Heart sounds, peripheral pulses, and edema
• Jugular venous distention
• Signs of anemia (pallor, tachycardia)
• Respiratory effort and lung sounds
• Mental status and signs of depression/anxiety
• Muscle strength and tone
• Deep tendon reflexes
• Gait and balance 1

Specialized Assessment for Cancer-Related Fatigue

For patients with cancer or cancer survivors:

• Use the Brief Fatigue Inventory (BFI) for more comprehensive assessment 2, 1
• Evaluate disease status and treatment history 2
• Assess for recurrence or progression of malignancy 2
• Review all medications, including over-the-counter and supplements 2, 1

Diagnostic Algorithm

1. For all patients with fatigue:

   • Start with CBC, CMP, thyroid function tests, and urinalysis 2, 1

2. If initial tests are normal but fatigue persists:

   • Add iron studies, vitamin D, and inflammatory markers 1
   • Do not repeat normal tests unless clinical status changes 3

3. If fatigue is accompanied by specific symptoms:

   • Shortness of breath or chest pain: Add BNP/NT-proBNP, ECG 1
   • Joint pain or rash: Add autoimmune markers 1
   • Weight loss or night sweats: Consider malignancy workup 2
   • Excessive sleepiness: Consider sleep study 1

Important Considerations

• Laboratory studies affect management in only about 5% of fatigue cases, so testing should be targeted rather than exhaustive 3
• Medication side effects are a commonly overlooked cause of fatigue 1
• Chronic fatigue lasting >6 months with normal initial workup rarely yields new findings on repeat testing 2, 3
• The diagnostic assessment should always include evaluation of emotional distress, sleep disturbance, pain, and activity level 2, 1

By following this structured approach to fatigue evaluation, clinicians can efficiently identify underlying causes while avoiding unnecessary testing, ultimately improving patient outcomes through targeted interventions.