What labs should be ordered immediately for a patient presenting with acute psychosis before initiating antipsychotic treatment in an inpatient psychiatric hospital?

Essential Laboratory Tests Before Starting Antipsychotic Treatment in Acute Psychosis

For patients presenting with acute psychosis in an inpatient psychiatric hospital, a focused medical assessment with targeted laboratory testing is recommended rather than routine extensive testing. 1

Core Laboratory Tests

First-Line Tests (Essential for All Patients)

• Complete blood count (CBC)
• Basic metabolic panel (BMP)/Comprehensive metabolic panel (CMP)
• Thyroid function tests (TSH, free T4)
• Urinalysis
• Urine toxicology screen

Second-Line Tests (Based on Clinical Presentation)

• Liver function tests (if not included in CMP)
• Pregnancy test (for women of childbearing age)
• Electrocardiogram (ECG) - especially if considering medications with risk of QTc prolongation

Patient-Specific Additional Testing

Age-Based Considerations

• Patients >65 years: More comprehensive laboratory evaluation including B12 levels 1, 2
• Children/Adolescents: Baseline liver and renal function tests 1

Clinical Presentation Indicators for Additional Testing

1. Abnormal vital signs: More extensive workup including electrolytes, CBC, and renal function 1, 2
2. Disorientation or confusion: Consider neuroimaging (CT/MRI) 1
3. First-episode psychosis: More comprehensive evaluation to rule out medical causes 1, 2
4. History of substance use: More extensive toxicology screening 2

Medical Conditions to Rule Out Before Antipsychotic Treatment

The following conditions can present with psychotic symptoms and must be considered:

Neurological Causes

• Stroke/TIA
• CNS hemorrhage or trauma
• Brain tumors or infections
• Seizure disorders
• Neurodegenerative disorders 1

Metabolic/Endocrine Causes

• Hypo/hyperglycemia
• Electrolyte disturbances (especially hyponatremia)
• Thyroid disorders
• Adrenal disorders 1

Other Medical Causes

• Medication side effects or interactions
• Substance intoxication or withdrawal
• Infections (especially UTI in elderly)
• Hypoxia 1, 2

Implementation Strategy

1. Order core laboratory tests immediately upon admission
2. Review medication history for potential drug interactions or medications that could cause psychotic symptoms
3. Perform targeted physical examination with focus on neurological, cardiac, and respiratory systems 1
4. Delay antipsychotic initiation until results of core laboratory tests are available when clinically feasible
5. Document baseline abnormal movements to avoid later mislabeling them as medication side effects 1

Common Pitfalls to Avoid

• Overreliance on routine testing: Studies show that less than 1 test in 50 results in clinically meaningful findings when ordered routinely rather than based on clinical presentation 1
• Attributing symptoms to psychiatric causes without adequate medical workup: Always consider medical causes of psychiatric symptoms 2
• Failure to recognize medication side effects or interactions: Consider medication effects when interpreting laboratory results 2
• Delaying treatment unnecessarily: While medical clearance is important, excessive testing can delay necessary psychiatric treatment 1

Special Considerations

• For acutely agitated patients requiring immediate intervention, consider benzodiazepines for initial management while awaiting laboratory results 3
• For first-episode psychosis, a more thorough medical workup is warranted as these patients have higher rates of medical conditions causing or contributing to psychotic symptoms 1, 2

Remember that the concept of "medical stability" (lack of medical conditions requiring acute evaluation/treatment) is more appropriate than "medical clearance" when determining readiness for psychiatric treatment 1.