Should I order bloodwork for this patient with migraines?

Bloodwork for Migraine Patients

For patients with typical migraine presentations and normal neurological examinations, routine bloodwork is generally not warranted or recommended. 1

Diagnostic Approach for Migraines

Clinical Diagnosis

• Migraine diagnosis is primarily clinical, based on history and physical examination using ICHD-3 criteria 1:
  • Recurrent headaches (at least 5 attacks)
  • Headache duration of 4-72 hours
  • At least 2 characteristics: unilateral location, pulsating quality, moderate/severe intensity, aggravation by activity
  • At least 1 associated symptom: nausea/vomiting, photophobia, phonophobia

When to Consider Laboratory Testing

Laboratory testing should be considered in the following scenarios:

1. Red Flag Symptoms 2, 1:

   • Thunderclap headache (sudden onset)
   • New onset after age 50
   • Progressively worsening headache pattern
   • Headache awakening patient from sleep
   • Headache worsened with Valsalva maneuver
   • Associated fever or neck stiffness
   • Focal neurological deficits
   • Unexplained systemic symptoms

2. Suspected Secondary Causes:

   • When clinical presentation suggests another underlying condition
   • Atypical features not consistent with primary migraine

Specific Laboratory Tests to Consider

When indicated by red flags or atypical presentation, consider:

1. Complete Blood Count (CBC):

   • To rule out infection or inflammatory conditions
   • To assess for anemia which can exacerbate headaches

2. Basic Chemistry Panel:

   • To evaluate for metabolic abnormalities
   • To check renal and hepatic function (especially before starting certain preventive medications)

3. Inflammatory Markers:

   • ESR/CRP if temporal arteritis or other inflammatory conditions are suspected (particularly in patients over 50)

4. Thyroid Function Tests:

   • If symptoms suggest thyroid dysfunction which can trigger headaches

Neuroimaging vs. Laboratory Testing

• Neuroimaging (CT/MRI) is more valuable than bloodwork for evaluating concerning headache presentations 2, 1
• Consider neuroimaging rather than bloodwork for:
  • Abnormal neurological examination
  • Headache worsened by Valsalva maneuver
  • Headache that awakens patient from sleep
  • New-onset headache in older adults
  • Progressively worsening headache pattern

Common Pitfalls to Avoid

1. Overutilization of Laboratory Tests:

   • Routine bloodwork in typical migraine presentations provides little diagnostic value
   • Unnecessary testing increases healthcare costs and patient anxiety

2. Underutilization in Atypical Cases:

   • Failing to order appropriate tests when red flags are present
   • Missing secondary causes of headache by assuming it's "just another migraine"

3. Relying Solely on Laboratory Results:

   • Laboratory tests rarely confirm migraine diagnosis
   • Normal laboratory results don't exclude secondary headache disorders

Clinical Decision Algorithm

1. Evaluate for typical migraine features using ICHD-3 criteria
2. Perform thorough neurological examination
3. Assess for red flags that suggest secondary headache
4. If typical migraine with normal exam and no red flags: No bloodwork needed
5. If red flags present or atypical features: Order targeted bloodwork based on specific concerns and consider neuroimaging

Remember that migraine is primarily a clinical diagnosis, and laboratory testing plays a limited role in typical presentations. The focus should be on accurate clinical assessment, identification of red flags, and appropriate treatment rather than routine bloodwork.