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

Laboratory Testing for Patients Presenting with Anxiety

Order TSH (thyroid-stimulating hormone) as the primary and essential laboratory test for all patients presenting with anxiety, and add free T4 only if TSH is abnormal or clinical suspicion for thyroid disease is high. 1

Core Laboratory Recommendation

• TSH is the single most important screening test for anxiety patients due to the significant comorbidity between anxiety disorders and thyroid dysfunction 1
• Free T4 (fT4) should be added selectively when TSH results are abnormal or when clinical findings strongly suggest thyroid disease 1
• The comorbidity between anxiety and thyroid disorders is substantial enough to warrant routine thyroid screening, with documented subclinical thyroid dysfunction showing blunted TSH responses and inverse relationships between anxiety levels and TSH 1

Additional Testing: Selective, Not Routine

Avoid routine extensive laboratory batteries for all anxiety patients. 1 The evidence from emergency medicine guidelines demonstrates that routine laboratory testing in psychiatric patients has extremely low yield, with studies showing that history and physical examination had 94% sensitivity for identifying medical conditions, while laboratory studies alone had only 20% sensitivity 2

When to Order Additional Tests

Order selective laboratory tests only when guided by specific clinical findings: 1

• First-time psychiatric presentation - consider broader medical workup 1
• Elderly patients - higher risk of medical causes 1
• Abnormal vital signs - pursue targeted testing based on abnormality 2
• New medical complaints - test according to specific symptoms 1
• Substance abuse history - consider toxicology screening and metabolic panel 2, 1
• Physical examination abnormalities - direct testing toward findings 2

Specific Additional Tests Based on Clinical Context

• Complete blood count - only if anemia or infection suspected clinically 2
• Comprehensive metabolic panel - only with medical symptoms, medication concerns, or vital sign abnormalities 2, 1
• Substance screening - when substance use disorder is suspected, as these commonly co-occur with anxiety 1
• Glucose - if metabolic symptoms present 2
• Pregnancy test - in reproductive-age females with relevant symptoms 2

Critical Pitfalls to Avoid

Do not order routine laboratory panels reflexively. Multiple studies in psychiatric emergency departments found that routine testing yielded clinically meaningful results in less than 1 test per 50 ordered, with false-positive results occurring 8 times more commonly than true-positive results 2. This leads to unnecessary follow-up testing and patient anxiety.

History and physical examination should drive testing decisions. Research demonstrates that 80% of medical conditions in psychiatric patients should be identified through history and physical examination alone 2. The Massachusetts ACEP guidelines emphasize that medical history, physical examination, and orientation testing are high yield, whereas routine laboratory testing is low yield for clinically significant conditions 2

Medical Causes to Consider

Investigate potential medical or substance-induced causes of anxiety symptoms, particularly: 1

• Thyroid dysfunction (hence the TSH requirement)
• Medication effects - corticosteroids, stimulants, bronchodilators
• Substance use or withdrawal - caffeine, alcohol, drugs
• Metabolic disturbances - only test when clinically indicated
• Cardiac conditions - only when symptoms suggest cardiac etiology

Practical Algorithm

1. All anxiety patients: Order TSH 1
2. If TSH abnormal: Add free T4 1
3. If clinical red flags present (abnormal vitals, medical symptoms, elderly, first presentation, substance history): Order targeted additional tests based on specific findings 2, 1
4. If young patient with known anxiety history, normal vitals, and no new medical symptoms: TSH alone is sufficient 2

This selective approach avoids the documented problem where 35% of emergency departments require mandatory testing regardless of presentation, despite evidence showing minimal clinical benefit 2.