What blood work would you order for someone with recurrent headaches?

Blood Work for Recurrent Headaches

For patients with recurrent headaches, a targeted blood panel should include complete blood count (CBC), comprehensive metabolic panel (CMP), thyroid function tests (TSH, free T4), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) to rule out secondary causes while prioritizing patient morbidity and mortality.

Initial Laboratory Evaluation

The laboratory workup for recurrent headaches should be guided by clinical suspicion of potential secondary causes, as most headaches are primary disorders that don't require extensive testing.

First-line Blood Tests:

• Complete Blood Count (CBC)

  • Screens for anemia, infection, and inflammatory conditions
  • Abnormal white blood cell counts may indicate infection or inflammation

• Comprehensive Metabolic Panel (CMP)

  • Evaluates kidney and liver function
  • Electrolyte imbalances can trigger or worsen headaches
  • Glucose levels to screen for diabetes-related headaches

• Thyroid Function Tests

  • TSH and free T4 to detect hypo/hyperthyroidism
  • Thyroid dysfunction can present with headache as demonstrated in case reports of painless thyroiditis 1

• Inflammatory Markers

  • Erythrocyte Sedimentation Rate (ESR)
  • C-Reactive Protein (CRP)
  • Particularly important in patients over 50 years to rule out temporal arteritis, which can be life-threatening if untreated 2

Additional Tests Based on Clinical Presentation

For Suspected Specific Conditions:

• For patients >50 years with new-onset headache:

  • ESR and CRP are mandatory to rule out temporal arteritis
  • ESR can be normal in 10-36% of patients with temporal arteritis, so clinical suspicion should guide management 2

• For headaches with orthostatic features:

  • Consider testing for intracranial hypotension 3
  • Note that rebound headaches after treatment of CSF leaks may present with reversed orthostatic symptoms (pain worse when lying down)

• For migraine with atypical features:

  • Consider more comprehensive testing to rule out secondary causes
  • The American Academy of Family Physicians recommends further investigation for headaches with atypical features 4

Clinical Considerations and Caveats

• Normal laboratory results are common: The yield of diagnostic testing in patients with recurrent headaches and normal neurological examinations is quite low 2, but testing remains important to rule out serious secondary causes

• Age matters: New-onset headaches in patients over 50 years warrant more extensive evaluation as up to 15% may have serious underlying pathology 2

• Red flags requiring more extensive workup:

  • Sudden onset "thunderclap" headache
  • Headache worsened with Valsalva maneuver
  • Abnormal neurological examination
  • Headache with systemic symptoms (fever, weight loss)
  • Headache pattern change or increasing severity

Diagnostic Algorithm

1. Obtain thorough headache history using ICHD-3 criteria to determine if primary or secondary headache is likely 3

2. Order baseline blood work:

   • CBC, CMP, TSH, free T4, ESR, CRP

3. For patients >50 years: Always include ESR and CRP even if clinical suspicion for temporal arteritis is low

4. If baseline tests are normal but symptoms persist:

   • Consider neuroimaging based on clinical presentation
   • The diagnostic yield of neuroimaging in patients with normal neurological examinations is low (brain tumors found in only 0.8% of cases) 2

5. For chronic migraine (≥15 headache days/month):

   • Consider additional testing to rule out medication overuse headache 3

Remember that while laboratory testing is important to rule out secondary causes, most recurrent headaches are primary headache disorders that will have normal blood work results. The primary goal is to identify potentially serious underlying conditions that could impact patient morbidity and mortality.