What initial laboratory tests are recommended for patients presenting with anxiety?

Laboratory Testing for Anxiety Disorders

Routine thyroid screening (TSH) should be performed when evaluating patients presenting with anxiety disorders, as there is significant comorbidity between anxiety and thyroid dysfunction. 1

Recommended Initial Laboratory Tests

Thyroid Function Testing

• TSH (thyroid-stimulating hormone) is the primary recommended screening test for patients with anxiety disorders 1
• Free T4 (fT4) should be added if TSH is abnormal or if clinical suspicion for thyroid disease is high 1
• The comorbidity between anxiety disorders and thyroid disorders is significant enough to warrant routine screening 1
• Subclinical thyroid dysfunction has been documented in anxiety patients, with blunted TSH responses and inverse relationships between anxiety levels and TSH 1

Selective Testing Based on Clinical Presentation

Laboratory testing beyond thyroid function should be guided by clinical evaluation rather than routine screening. 1

• Routine extensive laboratory batteries are not recommended for all anxiety patients 1
• Selective testing should be based on:
  • Patient history and physical examination findings 1
  • Presence of medical symptoms or vital sign abnormalities 1
  • First-time psychiatric presentation (higher likelihood of medical etiology) 1
  • Elderly patients, substance abuse history, or new medical complaints 1

Clinical Context and Pitfalls

Important Caveats About Thyroid Testing

• Up to one-third of psychiatric patients may show thyroid function test abnormalities that do not reflect true thyroid disease but rather represent "non-thyroidal illness" 2
• These abnormalities are secondary effects on the hypothalamic-pituitary-thyroid axis and usually resolve spontaneously 2
• Treatment of these non-thyroidal illness patterns may be unnecessary or potentially harmful 2
• Any abnormal thyroid results in psychiatric patients should be interpreted with skepticism and may require repeat testing 2

When Additional Testing May Be Indicated

• Medical or substance-induced causes of anxiety symptoms should be investigated 1
• Consider screening for substance use disorders, as these commonly co-occur with anxiety 1
• Age, sex, BMI, smoking status, and comorbid depression should be considered when interpreting results 1

Practical Approach

For a patient presenting with anxiety:

1. Obtain TSH as the primary screening test 1
2. Add free T4 if TSH is abnormal 1
3. Perform additional laboratory testing only when guided by specific clinical findings from history and physical examination 1
4. Avoid routine extensive laboratory panels, as false positives are 8 times more frequent than true positives 1
5. If thyroid abnormalities are detected, consider repeat testing to distinguish true thyroid disease from non-thyroidal illness 2

The evidence does not support routine screening beyond thyroid function unless specific clinical indicators are present. 1