What labs should be ordered for a patient with worsening tremor?

Laboratory Evaluation for Worsening Tremor

For patients with worsening tremor, essential laboratory tests should include thyroid function tests, comprehensive metabolic panel, complete blood count, ceruloplasmin, and liver function tests to rule out treatable causes of tremor. 1

Initial Laboratory Workup

First-line Laboratory Tests:

• Thyroid function tests (TSH, free T4): Hyperthyroidism and hypothyroidism can cause tremor 1
• Comprehensive metabolic panel: To assess:
  • Electrolytes (especially sodium, potassium, calcium, magnesium)
  • Glucose levels (diabetes can cause tremor)
  • Renal function (BUN, creatinine)
  • Liver function tests (AST, ALT, bilirubin)
• Complete blood count: To evaluate for anemia or infection
• Ceruloplasmin and serum copper: To rule out Wilson's disease, especially in patients under 40 years old 1
• HbA1c: To assess for diabetes mellitus 1

Second-line Laboratory Tests (Based on Clinical Suspicion):

• Urine albumin:creatinine ratio: If renal disease is suspected 1
• Serum drug levels: If on medications known to cause tremor
• Toxicology screen: If substance use or withdrawal is suspected
• Autoimmune markers: If autoimmune disease is suspected

Diagnostic Algorithm Based on Tremor Characteristics

For Resting Tremor (occurs when limb is relaxed):

• Focus on tests for parkinsonian disorders:
  • Consider dopamine transporter scan (DaTscan) if available 1
  • Copper studies to rule out Wilson's disease 1

For Action/Postural Tremor (occurs during voluntary movement):

• Focus on metabolic causes:
  • Thyroid function tests
  • Glucose/HbA1c
  • Electrolytes including calcium and magnesium
  • Liver function tests

For Sudden Worsening of Tremor:

• Drug levels (especially for medications that can cause tremor)
• Toxicology screen
• Electrolytes
• Thyroid function tests

Special Considerations

Age-specific Testing:

• Young patients (<40 years): Prioritize Wilson's disease testing (ceruloplasmin, serum copper, 24-hour urinary copper excretion, slit-lamp examination for Kayser-Fleischer rings) 1
• Middle-aged patients: Focus on thyroid disease, essential tremor, and medication effects
• Older patients: Consider vascular causes and neurodegenerative disorders

Red Flags Requiring Additional Testing:

• Asymmetric tremor: Consider structural brain imaging (MRI preferred over CT) 1
• Associated neurological symptoms: Consider MRI brain without contrast 1
• Rapid progression: Consider paraneoplastic panel, inflammatory markers

Imaging Considerations

• MRI brain: Recommended when there are additional neurological symptoms or signs beyond tremor 1
• CT head: If MRI is contraindicated; less sensitive but can still detect structural lesions 1
• DaTscan (Ioflupane SPECT/CT): Useful to differentiate parkinsonian syndromes from essential tremor 1

Common Pitfalls to Avoid

1. Missing Wilson's disease: Always check ceruloplasmin in young patients with tremor, as this is a treatable condition 1
2. Attributing tremor to anxiety: Ensure metabolic causes are ruled out before assuming psychological origin
3. Overlooking medication-induced tremor: Review all medications, including over-the-counter drugs
4. Incomplete thyroid testing: Both hyperthyroidism and severe hypothyroidism can cause tremor
5. Failing to consider alcohol withdrawal: In patients with history of alcohol use

By systematically evaluating these laboratory parameters, clinicians can identify treatable causes of tremor and guide appropriate management strategies for patients with worsening tremor symptoms.