What lab workup is recommended for patients presenting with anxiety and depression?

Laboratory Workup for Anxiety and Depression

Order TSH as the primary and essential laboratory test for all patients presenting with anxiety and depression, and add free T4 if TSH is abnormal. 1

Core Laboratory Testing

Thyroid Function Testing (Required)

• TSH (thyroid-stimulating hormone) is the mandatory screening test for patients presenting with anxiety and depression due to significant comorbidity between these psychiatric conditions and thyroid dysfunction 1
• Add free T4 (fT4) testing if TSH is abnormal or if clinical suspicion for thyroid disease is high based on symptoms such as weight changes, temperature intolerance, or fatigue 1
• The comorbidity between anxiety disorders and thyroid disorders is substantial enough to warrant routine screening in all cases 1
• Subclinical thyroid dysfunction has been documented in anxiety patients, with blunted TSH responses and inverse relationships between anxiety levels and TSH 1

Selective Additional Testing

When to Order Beyond Thyroid Function

Do not order routine extensive laboratory batteries for all anxiety and depression patients. 1 Additional testing should only be pursued when specific clinical indicators are present:

• First-time psychiatric presentation in a patient with no prior mental health history 1
• Elderly patients (age >65) presenting with new-onset psychiatric symptoms 1
• Presence of medical symptoms or vital sign abnormalities such as tachycardia, hypertension, fever, or unexplained weight loss 1
• History of substance abuse or current substance use concerns 1
• New medical complaints accompanying psychiatric symptoms 1

Medical Causes to Investigate

• Screen for substance use disorders as these commonly co-occur with anxiety and depression 1
• Consider medical or substance-induced causes of symptoms, taking into account age, sex, BMI, smoking status, and comorbid depression 1

Clinical Assessment Framework

Initial Screening Tools

• Use PHQ-9 as the primary screening tool for depressive symptoms 2
• Use GAD-7 as the primary screening tool for anxiety symptoms 2
• These validated scales provide reportable scores with established clinical cut-offs 2

Risk Stratification Based on Screening Scores

For Depression (PHQ-9):

• Scores ≥10 indicate moderate to severe depression requiring further diagnostic assessment 2

For Anxiety (GAD-7):

• Scores 0-4: None/mild symptoms 2
• Scores 5-9: Moderate symptoms 2
• Scores 10-14: Moderate to severe symptoms 2
• Scores 15-21: Severe symptoms requiring referral to mental health professionals 2

Critical Safety Assessment

Immediate Actions Required

• Assess for risk of harm to self or others at initial presentation - this takes priority over all laboratory testing 2
• If suicidal ideation, self-harm risk, or harm to others is identified, refer immediately for emergency psychiatric evaluation 2
• Facilitate a safe environment and one-to-one observation while awaiting emergency evaluation 2

Common Pitfalls to Avoid

Over-Testing

• Avoid ordering comprehensive metabolic panels, complete blood counts, or other routine laboratory tests without specific clinical indications 1
• Extensive laboratory batteries are not cost-effective and rarely change management in the absence of specific clinical findings 1

Under-Recognition of Medical Causes

• First, treat medical causes of depressive symptoms such as unrelieved pain, fatigue, or delirium from infection or electrolyte imbalance before attributing symptoms solely to psychiatric illness 2
• Medical or substance-induced causes (such as interferon administration, corticosteroids, or thyroid dysfunction) should be determined and treated 2

Missing Comorbidity

• Up to 85% of patients with depression have significant anxiety, and 90% of patients with anxiety disorder have depression 3
• Comorbid anxiety and depression occur in up to 25% of general practice patients 3
• Patients with comorbidity typically suffer greater impairment and may be at higher risk for suicide 4, 5

Practical Algorithm

1. Screen with PHQ-9 and GAD-7 at initial presentation 2
2. Order TSH on all patients 1
3. Add free T4 if TSH is abnormal 1
4. Order additional labs only if:
   • First psychiatric presentation 1
   • Age >65 1
   • Abnormal vital signs or physical exam findings 1
   • Substance abuse history 1
   • New medical complaints 1
5. Assess for medical causes of symptoms including pain, fatigue, infection, or medication effects 2
6. Refer for further diagnostic assessment if moderate to severe symptoms are detected on screening tools 2