What additional testing is needed to rule out other disorders in a patient presenting with symptoms suggestive of panic disorder?

Laboratory Testing to Rule Out Medical Disorders in Panic Disorder

Obtain TSH on all patients presenting with panic disorder symptoms, and add free T4 only if TSH is abnormal or clinical suspicion for thyroid disease is high. 1

Essential Thyroid Screening

• TSH is the single most important and only routinely recommended laboratory test for panic disorder evaluation 1
• Free T4 should be added selectively when TSH is abnormal or when clinical features suggest thyroid disease (such as heat/cold intolerance, weight changes, tremor, or goiter) 1
• The rationale is strong: 2-9% of panic disorder patients have comorbid thyroid disease, with higher rates in females 2, 1
• Thyroid dysfunction can both mimic and exacerbate panic symptoms because thyroid hormone receptors are present throughout the limbic system that regulates anxiety 1

What NOT to Test Routinely

• Extensive screening for pheochromocytoma, hypoglycemia, and Cushing's disease is not recommended as routine practice due to low yield and cost-ineffectiveness 1, 3
• These conditions are exceedingly rare causes of panic symptoms, and routine screening is not justified without specific clinical indicators 3

Selective Additional Testing Based on Red Flags

Obtain additional laboratory tests only when the following clinical red flags are present 1:

• New onset panic symptoms in elderly patients (age >60) - consider broader medical workup
• First-time psychiatric presentation with atypical features
• Vital sign abnormalities (persistent tachycardia, hypertension, fever)
• Concurrent medical symptoms beyond typical panic (weight loss, heat intolerance, headaches, flushing episodes)

Substance Use Screening

• Consider urine drug screening when history suggests alcohol or drug abuse, as these commonly co-occur with panic disorder 2, 1
• Substance use disorders are a pertinent risk factor that should be identified during assessment 2

Common Pitfalls to Avoid

• Do not pursue exhaustive medical testing without clinical indicators beyond the panic symptoms themselves - this leads to unnecessary costs, patient anxiety, and false positive results 1
• Do not assume all panic-like symptoms are medical until proven otherwise - panic disorder is far more common than conditions like pheochromocytoma 3
• Do not order "routine panic panels" - there is no evidence-based panel beyond TSH 1

Practical Testing Algorithm

1. All patients: Obtain TSH at initial evaluation 1
2. If TSH abnormal: Add free T4 1
3. If clinical red flags present (elderly onset, vital sign abnormalities, concurrent medical symptoms): Consider targeted testing based on specific findings 1
4. If substance use suspected: Obtain urine drug screen 1
5. Otherwise: No additional laboratory testing is indicated 1, 3