Best Practices for Laboratory Testing in Psychiatric Settings
Routine laboratory testing of all psychiatric patients is of very low yield and should be directed by the history and physical examination rather than performed as standard practice. 1
Evidence-Based Approach to Laboratory Testing
Initial Assessment
Laboratory testing in psychiatric settings should follow a targeted approach based on:
- Patient's clinical presentation
- Medical history
- Medication regimen
- Physical examination findings
Recommended Laboratory Testing Framework
For All New Psychiatric Patients:
- Directed testing only - Laboratory evaluation should be guided by clinical findings rather than routine panels 1
- Avoid extensive routine testing - False positive results are 8 times more common than true positives in psychiatric patients 2
For Specific Patient Populations:
Higher-risk groups that warrant more comprehensive laboratory evaluation include:
- Patients >65 years of age
- First-episode psychosis
- History of substance use disorders
- Disoriented patients
- Patients with abnormal vital signs
- Patients with medical comorbidities
- Patients on psychotropic medications requiring monitoring
Laboratory Tests by Clinical Scenario
1. Initial Psychiatric Evaluation
For alert, cooperative patients with normal vital signs and noncontributory history/physical examination:
- No routine laboratory testing needed 1
- Consider targeted testing based on specific symptoms or risk factors
For patients with first-episode psychiatric symptoms:
- Basic metabolic panel
- Complete blood count
- Thyroid function tests
- Urinalysis
- Consider toxicology screen if substance use suspected
2. Medication Monitoring
For patients on psychotropic medications:
- Therapeutic drug monitoring (TDM) for medications with established therapeutic windows 3
- Medication-specific monitoring:
- Lithium: Serum levels, renal and thyroid function
- Valproate: Serum levels, liver function, CBC
- Clozapine: CBC with differential (due to risk of severe neutropenia) 4
- Antipsychotics: Metabolic panel, lipid profile, glucose
3. Medical Clearance in Emergency Settings
For psychiatric patients in emergency departments:
- Laboratory testing should be directed by history and physical examination 1
- Urine drug screens have limited utility in altering immediate management 1
- Consider basic metabolic panel, glucose, and targeted testing based on clinical presentation
Common Pitfalls to Avoid
Overreliance on laboratory testing - Most abnormal results can be predicted by history and physical examination 5
Attributing behavioral changes to psychiatric causes without adequate medical workup - Always consider medical causes of psychiatric symptoms 6
Routine ordering of extensive test panels - This leads to many clinically insignificant findings that don't affect patient management 5
Failure to recognize medication side effects or interactions - Consider medication effects when interpreting laboratory results 6
Efficient Testing Strategy
A more efficient testing approach would include:
- For women: 9 targeted tests based on clinical presentation 2
- For men: 13 targeted tests based on clinical presentation 2
- For all patients: Consider serum glucose, BUN, creatinine, and urinalysis as the few tests with merit as broader screening tests in asymptomatic patients 5
Special Considerations
Therapeutic Drug Monitoring (TDM) is valuable for dose optimization, especially with uncertain drug adherence, suboptimal tolerability, non-response at therapeutic doses, or pharmacokinetic drug-drug interactions 3
Patient populations that benefit most from TDM include children, pregnant women, elderly patients, individuals with intellectual disabilities, forensic patients, and those with known or suspected pharmacokinetic abnormalities 3
Laboratory alert levels should be established for medications, requiring immediate notification of the treating physician when exceeded 3
By following these evidence-based guidelines for laboratory testing in psychiatric settings, clinicians can provide more efficient and cost-effective care while still ensuring appropriate medical evaluation of psychiatric patients.