What initial laboratory tests are recommended for a child or adolescent being evaluated for anxiety and/or depression before starting pharmacologic treatment?

Laboratory Testing for Pediatric Anxiety and Depression

Before initiating psychotropic medication in children and adolescents with anxiety or depression, obtain a targeted medical history and perform selective laboratory testing based on clinical findings rather than ordering a routine battery of tests for all patients. 1

Core Principle: History-Guided Testing

The American Academy of Child and Adolescent Psychiatry emphasizes that a comprehensive medical evaluation should be driven by the patient's history, physical examination, and vital signs rather than reflexive laboratory panels. 1 This approach maximizes diagnostic yield while minimizing unnecessary testing and cost.

Essential Pre-Treatment Assessment

Medical History Components

Before prescribing any psychotropic medication, document the following:

• Current and past medical problems that could account for psychiatric symptoms 1
• All medications including prescribed drugs, over-the-counter preparations, complementary/alternative treatments, and illicit substances 1
• Medication allergies and adverse reactions 1
• Personal history of structural cardiac abnormalities (especially before stimulants) or metabolic conditions 1
• Family history of malignant arrhythmias, sudden cardiac death, or medical problems associated with increased medication side-effect risk 1

Baseline Physical Measurements

• Height and weight should be documented before starting any psychotropic medication, particularly stimulants and antipsychotics 1
• Vital signs including heart rate, blood pressure, and temperature to identify abnormalities suggesting medical causes 1

Selective Laboratory Testing Based on Clinical Presentation

Rule Out Medical Mimics First

The American Academy of Child and Adolescent Psychiatry identifies specific medical conditions that must be excluded when anxiety or depression symptoms are present:

Endocrine disorders:

• Thyroid function tests (TSH, free T4) if hyperthyroidism or hypothyroidism is suspected based on symptoms such as tremor, heat/cold intolerance, weight changes, or tachycardia 1, 2
• Glucose testing if hypoglycemia symptoms (shakiness, sweating, confusion) are present 2

Cardiac conditions:

• Electrocardiogram (ECG) if palpitations, chest pain, syncope, or family history of sudden cardiac death are reported 2

Substance-related causes:

• Urine toxicology screen only when history or physical examination suggests substance use—routine screening in all psychiatric patients has minimal utility and rarely changes management 1
• One study found that routine toxicology screens were positive in only 5% of cases and resulted in zero changes to patient management 1

Other targeted tests:

• Complete blood count if infection, anemia, or systemic illness is suspected 1
• Comprehensive metabolic panel if electrolyte disturbances, renal dysfunction, or metabolic abnormalities are suggested by history 1

What NOT to Do

Avoid Routine Laboratory Batteries

• Do not order predetermined panels of tests for all pediatric patients presenting with anxiety or depression 1
• Studies demonstrate that routine medical screening in alert, cooperative patients with normal vital signs and unremarkable history/physical examination is low-yield and costly 1
• The American College of Emergency Physicians recommends "focused medical assessment" rather than blanket testing protocols 1

Specific Testing to Avoid Unless Clinically Indicated

• Routine urine drug screens in the absence of clinical suspicion—these are frequently ordered due to protocol rather than medical necessity and rarely alter management 1
• Serum alcohol levels without clinical indication 1
• Extensive metabolic panels in asymptomatic patients 1

Pre-Medication Baseline Testing

For Specific Medication Classes

When pharmacotherapy is planned, certain baseline measurements are appropriate:

• Lipid panel before initiating atypical antipsychotics (if used for severe anxiety or comorbid conditions) 1
• Baseline ECG may be considered before stimulants in patients with cardiac risk factors, though not universally required 1
• Liver function tests are not routinely needed before SSRIs unless hepatic disease is suspected 1

Clinical Algorithm

Step 1: Conduct thorough history and physical examination with attention to vital signs, neurologic findings, and cardiac/respiratory systems 1

Step 2: Order laboratory tests only if history or examination suggests specific medical conditions:

• Thyroid dysfunction → TSH, free T4
• Cardiac concerns → ECG
• Substance use suspected → targeted toxicology
• Systemic illness → CBC, metabolic panel

Step 3: Document baseline height, weight, and vital signs before any medication 1

Step 4: Add medication-specific baseline testing only when pharmacotherapy is planned (e.g., lipids before antipsychotics) 1

Common Pitfalls to Avoid

• Missing medical mimics by failing to consider hyperthyroidism, hypoglycemia, cardiac arrhythmias, or substance use as causes of anxiety symptoms 2, 3
• Over-testing with routine panels that waste resources and delay psychiatric treatment 1
• Under-documenting baseline physical measurements that are essential for monitoring medication effects 1
• Ordering tests "just to be safe" without clinical justification—this approach has been shown to have minimal diagnostic yield 1

Coordination of Care

• Communicate with the patient's pediatrician to obtain recent medical evaluations and avoid duplicating recent laboratory work 1
• Document that medical screening has been completed to reassure patients, families, and prescribers before initiating psychiatric treatment 1
• Establish monitoring protocols with other professionals (school nurses, primary care physicians) for ongoing medication management 1