What laboratory tests should be ordered for a patient with severe anxiety?

Laboratory Tests for Severe Anxiety

For patients with severe anxiety, a targeted laboratory workup should include thyroid function tests (TSH, free T3, free T4), complete blood count, comprehensive metabolic panel, vitamin B12 levels, and folate levels to rule out medical causes that could be contributing to anxiety symptoms.

Initial Assessment Framework

Before ordering laboratory tests, use validated screening tools to confirm and quantify anxiety severity:

• GAD-7 scale: Most validated tool for assessing anxiety severity 1

  • 0-4: Minimal anxiety
  • 5-9: Mild anxiety
  • 10-14: Moderate anxiety
  • 15-21: Severe anxiety

• Alternative assessment tools:

  • Hospital Anxiety and Depression Scale (HADS) - particularly useful when medical conditions may confound physical symptoms 1
  • Beck Anxiety Inventory (BAI) - focuses on somatic symptoms 2

Recommended Laboratory Tests

First-line Tests

1. Thyroid Function Tests:

   • TSH, free T3, free T4 2
   • Rationale: Thyroid dysfunction can mimic or exacerbate anxiety symptoms

2. Complete Blood Count (CBC):

   • To evaluate for anemia or infection that may contribute to anxiety symptoms

3. Comprehensive Metabolic Panel:

   • Includes glucose, electrolytes, kidney and liver function
   • Rationale: Metabolic abnormalities can present with anxiety symptoms

4. Vitamin B12 and Folate Levels:

   • Lower vitamin B12 levels correlate with higher risk of severe anxiety symptoms 3
   • Folate deficiency has been found in 10.2% of adolescents with anxiety symptoms 3

Second-line Tests (Based on Clinical Suspicion)

1. Homocysteine Levels:

   • Elevated in 25.8% of patients with anxiety symptoms 3
   • Associated with B12 and folate deficiency

2. Inflammatory Markers:

   • C-reactive protein (CRP)
   • Interleukin-6 (IL-6)
   • Tumor necrosis factor-α (TNF-α)
   • Rationale: Inflammation may play a role in anxiety disorders 4, 3

3. Toxicology Screen:

   • Particularly important if substance use is suspected
   • Alcohol, stimulants, and other substances can cause or worsen anxiety

Evidence-Based Approach to Laboratory Testing

The approach to laboratory testing should be selective rather than routine for all patients. Multiple studies have shown that routine extensive laboratory testing has low yield and high rates of false positives 2.

When to Order Comprehensive Testing:

• New-onset anxiety without prior psychiatric history
• Atypical presentation or sudden change in symptoms
• Presence of medical complaints or abnormal vital signs
• Elderly patients
• Patients with substance abuse history
• Lower socioeconomic status patients 2

When Limited Testing May Be Sufficient:

• Young patients with typical anxiety symptoms
• Previous well-documented anxiety disorder with similar presentation
• No medical comorbidities or abnormal vital signs

Common Pitfalls to Avoid

1. Failing to consider medical causes: Always rule out medical conditions that can present with anxiety symptoms, including thyroid disorders, caffeine excess, hypoglycemia, cardiac conditions, and medication side effects 1

2. Over-testing: Extensive, routine laboratory testing for all patients with anxiety is unnecessary and can lead to false positives (8 times more frequent than true positives) 2

3. Under-testing: Patients with new psychiatric symptoms, especially first presentations, require careful evaluation for medical illness 2

4. Missing comorbid depression: Anxiety and depression frequently co-occur; consider screening with PHQ-9 alongside anxiety assessment 1, 5

By following this targeted approach to laboratory testing, clinicians can efficiently identify medical conditions that may be causing or exacerbating anxiety symptoms while avoiding unnecessary testing.