What laboratory tests are recommended for a new diagnosis of generalized anxiety with the initiation of a new medication, such as sertraline (Selective Serotonin Reuptake Inhibitor) or fluoxetine (Selective Serotonin Reuptake Inhibitor)?

Laboratory Tests for a New Diagnosis of Generalized Anxiety Disorder with Medication Initiation

For a new diagnosis of generalized anxiety disorder with initiation of medication therapy such as an SSRI, minimal laboratory testing is required as there is no specific diagnostic test for anxiety disorders.

Initial Diagnostic Assessment

• The GAD-7 scale is a validated diagnostic tool for generalized anxiety disorder in primary care settings. A score of ≥9 points has a positive likelihood ratio of 4.3 and is considered a positive screen 1.
• The GAD-2, consisting of the first two questions of the GAD-7, can be used as an ultra-short diagnostic tool with a cutoff score of ≥3 indicating possible anxiety disorder 1.

Recommended Laboratory Tests Before Starting SSRIs

Basic Laboratory Tests:

• Complete blood count (CBC) to establish baseline health status 1
• Basic metabolic panel to assess kidney function and electrolytes 1
• Liver function tests to establish baseline liver function, especially important as SSRIs are metabolized by the liver 1
• Thyroid function tests (TSH) to rule out thyroid disorders that can mimic anxiety symptoms 1

Additional Considerations:

• Electrocardiogram (ECG) should be considered for patients with cardiac risk factors, especially if prescribing citalopram, which may cause QT prolongation at doses exceeding 40 mg/day 1
• Pregnancy test for women of childbearing age before starting SSRIs 1

Medication-Specific Considerations

For Sertraline:

• Monitor prothrombin time if patient is on warfarin or other anticoagulants due to potential drug interactions 2
• No specific additional laboratory monitoring is required for sertraline beyond baseline tests 2, 3

For Fluoxetine:

• May have advantages in terms of response and remission rates for generalized anxiety disorder 4
• Similar laboratory monitoring as other SSRIs 1

Ongoing Monitoring

• No routine laboratory monitoring is required during SSRI treatment unless clinically indicated 1
• Regular assessment of treatment response using standardized symptom rating scales like the GAD-7 is recommended 1

Special Considerations

• Drug-drug interactions: SSRIs may interact with drugs metabolized by CYP450 enzymes. Citalopram/escitalopram may have the least effect on CYP450 isoenzymes compared to other SSRIs 1
• Bleeding risk: Monitor patients on concomitant NSAIDs, aspirin, or warfarin due to increased bleeding risk 2
• Serotonin syndrome: Be cautious when combining SSRIs with other serotonergic medications 1

Key Points to Remember

• There are no specific biological markers currently validated for diagnosing anxiety disorders in routine clinical practice 5
• Laboratory tests are primarily used to rule out medical conditions that can mimic anxiety symptoms rather than to diagnose anxiety disorders 1
• SSRIs are generally well-tolerated with minimal need for laboratory monitoring beyond initial baseline tests 1, 3

Common Pitfalls to Avoid

• Overreliance on laboratory tests: Anxiety disorders are clinical diagnoses; laboratory tests cannot confirm the diagnosis 1
• Inadequate screening: Using validated tools like GAD-7 improves diagnostic accuracy 1
• Overlooking medical causes: Thyroid disorders, cardiac conditions, and substance use can present with anxiety symptoms 1
• Neglecting drug interactions: Always check for potential interactions before starting SSRIs 2