What diagnostic tests are recommended for a patient presenting with fatigue, nausea, and headaches?

Diagnostic Approach for Fatigue, Nausea, and Headaches

For a patient presenting with fatigue, nausea, and headaches, a comprehensive laboratory evaluation should be performed including complete blood count, comprehensive metabolic panel, thyroid function tests, and inflammatory markers to identify the underlying cause.

Initial Assessment

Fatigue Assessment

• Use a numeric rating scale (0-10) to quantify fatigue severity 1, 2:
  • Mild: 1-3
  • Moderate: 4-6
  • Severe: 7-10
• For moderate to severe fatigue (score ≥4), proceed with comprehensive evaluation 1
• Document onset, pattern, duration, and alleviating/worsening factors 1

Headache Assessment

• Characterize headache features 1:
  • Location (one/both sides, front/back, over/behind eyes)
  • Duration (hours, days)
  • Associated symptoms (visual changes, photophobia, nausea)
  • Timing (morning, evening, awakens from sleep)
  • Triggers (stress, foods, weather, odors)
  • Exacerbating factors (Valsalva maneuver, position changes)

Nausea Assessment

• Document onset, frequency, severity, and relation to meals 1
• Identify associated symptoms (vomiting, abdominal pain)
• Note alleviating or aggravating factors

Laboratory Evaluation

Essential Laboratory Tests

1. Complete Blood Count (CBC) 2, 3, 4, 5:

   • Evaluate for anemia, infection, or inflammation
   • Assess white blood cell count and differential
   • Check platelet count for thrombocytopenia/thrombocytosis

2. Comprehensive Metabolic Panel (CMP) 2:

   • Assess electrolyte imbalances
   • Evaluate kidney and liver function
   • Check blood glucose levels

3. Thyroid Function Tests 1, 2:

   • TSH and free T4
   • Rule out hypothyroidism or hyperthyroidism

4. Inflammatory Markers 2:

   • Erythrocyte sedimentation rate (ESR)
   • C-reactive protein (CRP)

Additional Tests Based on Clinical Suspicion

1. Iron Studies 2:

   • Serum iron, ferritin, total iron binding capacity (TIBC)
   • Evaluate for iron deficiency anemia

2. Vitamin D Level 2:

   • Particularly in patients with chronic fatigue

3. Morning Cortisol and ACTH 1, 2:

   • Rule out adrenal insufficiency
   • Especially important if patient is on or recently completed immunotherapy

4. Urinalysis 2:

   • Evaluate for kidney function and infection
   • Check for protein, blood, and glucose

Specialized Testing Based on Clinical Findings

For Suspected Endocrine Disorders

• If thyroid dysfunction is suspected, check thyroid antibodies (TPO) 1
• For suspected hypophysitis (especially in patients on immunotherapy), consider MRI of the sella with pituitary cuts 1

For Suspected Neurological Disorders

• If headaches have concerning features (severe, sudden onset, worsened with Valsalva, awakens from sleep), consider neuroimaging 1
• For suspected meningitis or encephalitis, consider lumbar puncture 1

For Suspected Cardiac Issues

• If fatigue is associated with exertion or dyspnea, consider BNP or NT-proBNP 2
• ECG may be indicated based on clinical suspicion 1

Specific Scenarios to Consider

Immune-Related Adverse Events

• For patients on immune checkpoint inhibitors, consider hypophysitis which can present with headache (85%), fatigue (66%), and various degrees of anterior pituitary hormone deficiency 1
• Check morning ACTH and cortisol, TSH and free T4, gonadal hormones 1

Cancer-Related Fatigue

• For patients with history of cancer, evaluate for recurrence or treatment-related effects 1
• Consider specific cancer-related fatigue scales like Brief Fatigue Inventory (BFI) or Functional Assessment of Cancer Therapy-Fatigue (FACT-F) 2

Infectious Causes

• Consider viral panels, particularly if symptoms are acute in onset
• Check for signs of chronic infections that can cause fatigue

Management Approach

1. Treat Identified Underlying Causes:

   • Correct anemia, electrolyte imbalances, or hormonal deficiencies
   • Address infections if present
   • Manage any metabolic disorders

2. Symptomatic Management:

   • For headaches: appropriate analgesics based on severity and type
   • For nausea: antiemetics as needed
   • For fatigue: address sleep hygiene, consider physical activity as tolerated 1

3. Follow-up:

   • Reassess symptoms after treating identified causes
   • Consider specialist referral if symptoms persist despite initial management

Common Pitfalls to Avoid

• Overlooking medication side effects as a cause of fatigue, nausea, and headaches 2
• Failing to assess for depression or anxiety, which can manifest with these symptoms
• Missing subtle thyroid dysfunction by only checking TSH without free T4
• Attributing symptoms to stress without adequate workup
• Focusing on only one symptom rather than considering the constellation of symptoms together

By following this systematic approach, you can efficiently identify the underlying cause of fatigue, nausea, and headaches and provide appropriate management for your patient.