What laboratory tests are initially recommended for a patient presenting with dizziness?

Initial Laboratory Testing for Patients Presenting with Dizziness

For patients presenting with dizziness, initial laboratory testing should be targeted based on clinical presentation rather than performed as a comprehensive panel, with serum glucose being the most essential test for all patients.1

Recommended Initial Laboratory Tests

Essential Tests for All Patients with Dizziness:

• Serum glucose - Critical for all patients as hypoglycemia can present with dizziness and is occasionally found unexpectedly 1
• Basic electrolytes (particularly sodium, potassium) - To detect hyponatremia, which may contribute to dizziness 1

Tests to Consider Based on Clinical Presentation:

• Complete blood count - To evaluate for anemia or infection
• Blood urea nitrogen and creatinine - To assess renal function
• Thyroid-stimulating hormone - For suspected thyroid dysfunction
• Pregnancy test - For women of childbearing age 1
• Calcium and magnesium levels - If clinically indicated (not routinely recommended) 1
• Liver function tests - For patients with suspected alcohol-related issues 1
• Drug screen - When medication side effects are suspected 1

Clinical Decision-Making Algorithm

1. Categorize the dizziness based on timing and triggers:

   • Acute vestibular syndrome (continuous dizziness)
   • Spontaneous episodic vestibular syndrome (recurrent unprovoked episodes)
   • Triggered episodic vestibular syndrome (positional/situational triggers) 2

2. For acute vestibular syndrome:

   • Perform HINTS exam (Head Impulse test, Nystagmus, Test of Skew)
   • Order glucose and basic electrolytes for all patients
   • Consider additional testing based on clinical suspicion 1

3. For suspected BPPV:

   • Perform Dix-Hallpike and supine roll tests
   • Laboratory testing is generally low-yield if diagnosis is clear 3

4. For patients with risk factors or concerning features:

   • Age ≥45 years: Consider cardiac monitoring 4
   • Neurological deficits: More comprehensive testing and neuroimaging
   • Medication use: Consider drug levels if relevant
   • Known medical conditions: Target testing to specific conditions 1

Important Considerations

• The history and physical examination predict the majority of patients who will have laboratory abnormalities 1
• Routine extensive laboratory testing in otherwise healthy patients with clear peripheral causes of dizziness (e.g., BPPV) has low yield 3
• Glucose testing is supported for all dizzy patients regardless of presentation 4
• Cardiac rhythm monitoring is recommended for patients aged 45 and older 4

Common Pitfalls to Avoid

• Over-reliance on laboratory testing - The HINTS examination is more valuable than laboratory testing for distinguishing between benign peripheral causes and potentially life-threatening central causes of vertigo 1
• Under-testing in high-risk patients - Older patients and those with neurological deficits require more comprehensive evaluation 1
• Missing central causes - Posterior circulation stroke can present with isolated vertigo in up to 25% of cases, with prevalence increasing to 75% in high vascular risk cohorts 1
• Unnecessary extensive testing - Multiple studies show that selective testing based on clinical presentation is more appropriate than routine comprehensive panels 3

Remember that laboratory testing should complement, not replace, a thorough clinical assessment. The most important diagnostic tools remain a detailed history and targeted physical examination, with laboratory tests serving to confirm clinical suspicions or rule out specific conditions.