What laboratory tests are necessary for a patient presenting with anxiety?

Laboratory Testing for Anxiety Disorders

For patients presenting with anxiety, obtain TSH as the primary and only routine screening test; additional laboratory testing should be guided exclusively by specific clinical findings from history and physical examination, not by blanket protocols. 1

Recommended Routine Testing

• TSH (thyroid-stimulating hormone) is the single mandatory screening test for all patients presenting with anxiety disorders, as thyroid dysfunction significantly comorbidities with anxiety and can directly cause or exacerbate anxiety symptoms 2, 1
• Add free T4 only if TSH is abnormal or if clinical examination reveals specific signs of thyroid disease (tremor, heat/cold intolerance, weight changes, tachycardia) 1
• The comorbidity between anxiety and thyroid disorders, including subclinical dysfunction with blunted TSH responses, justifies this focused screening approach 1

What NOT to Order Routinely

• Do not order routine comprehensive metabolic panels, complete blood counts, liver function tests, or extensive laboratory batteries in alert, cooperative patients with normal vital signs and noncontributory history/physical examination 2
• Routine urine drug screens have extremely low yield (only 5% positive) with no management changes in patients without specific substance use concerns 2, 3
• False positives from blanket testing are 8 times more common than true positives (1.8%) when history and physical examination are normal 3
• History and physical examination alone have 94% sensitivity for identifying medical conditions requiring testing, making reflexive laboratory ordering counterproductive 2, 4

Selective Testing Based on Clinical Red Flags

Order additional tests only when specific clinical indicators are present:

• Serum glucose: Only if hypoglycemia or hyperglycemia is suspected based on polyuria, polydipsia, altered mental status, or known diabetes 3
• Electrolytes (comprehensive metabolic panel): Only when medication use (diuretics, lithium), excessive water intake, or clinical presentation (confusion, weakness) suggests metabolic disturbance 3
• Complete blood count: Only when infection is suspected based on fever, immunocompromised status, or signs of systemic illness 3
• Urine toxicology screen: Only in patients with substance abuse history, altered mental status unexplained by psychiatric history, or when disposition/treatment planning requires confirmation 4
• Hepatic panel: Only in patients with polysubstance use disorder, alcohol abuse history, or clinical signs of liver disease 4

Special Populations Requiring Lower Testing Threshold

• Elderly patients (≥65 years): Consider targeted evaluation including TSH, vitamin B12, urinalysis, and comprehensive metabolic panel, as medical causes of psychiatric symptoms are more common in this age group 3
• First psychiatric presentation: More thorough evaluation warranted to exclude organic causes 2
• Patients with substance abuse history: Comprehensive metabolic panel, glucose, TSH, and hepatic panel are appropriate given higher risk of metabolic derangements 4
• Abnormal vital signs: Any vital sign abnormality mandates investigation for underlying medical causes before attributing symptoms to anxiety alone 2, 4

Medical Conditions That Can Masquerade as Anxiety

Be alert for these conditions based on history and examination findings:

• Endocrine: Hyperthyroidism, hypoglycemia, pheochromocytoma, Cushing disease 2
• Cardiac: Arrhythmias, valvular disease 2
• Respiratory: Hypoxia, asthma exacerbation 2
• Neurologic: Seizures, migraine, CNS lesions 2
• Toxic/metabolic: Caffeinism, medication effects (steroids, decongestants), substance withdrawal 2

Critical Clinical Approach

• The diagnostic evaluation must be directed by history and physical examination findings, not routine blanket testing protocols 2, 3
• Careful assessment of vital signs, complete neurologic examination, and attention to cardiac and respiratory systems are more valuable than laboratory panels 2
• When medical symptoms or vital sign abnormalities are present, targeted testing based on specific clinical suspicion is appropriate 2
• Collaborate with the patient's primary care practitioner when ordering tests to avoid duplication and ensure appropriate follow-up 2

Common Pitfalls to Avoid

• Do not order extensive laboratory panels "just to be safe" in patients with normal vital signs and unremarkable history/physical examination—this increases false positives without improving outcomes 2, 3
• Do not assume routine urine drug screens are helpful—they rarely change management unless substance use is specifically suspected 2, 3
• Do not skip the thyroid screening—this is the one test with sufficient yield to justify routine use 1
• Do not ignore abnormal vital signs—any vital sign abnormality requires investigation before attributing symptoms purely to anxiety 2, 4