Laboratory Testing for Psychiatric Patients to Rule Out Organic Disease
Routine laboratory testing should NOT be performed in alert, cooperative psychiatric patients with normal vital signs and a noncontributory history and physical examination—instead, diagnostic evaluation should be directed by clinical findings from history and physical examination. 1
General Approach: Selective Testing Based on Clinical Assessment
The evidence strongly supports a selective, clinically-guided approach rather than routine screening panels 1:
- False positives outnumber true positives 8:1 when routine laboratory testing is performed in psychiatric patients with normal clinical assessments 1
- Only 1.1% of investigations yield clinically significant findings that change diagnosis or management in psychiatric patients 2
- In contrast, history yields 15.6% and physical examination yields 14.9% of clinically significant findings 2
- Most abnormal laboratory results (when found) are clinically insignificant and do not affect patient management 1, 3
High-Risk Populations Requiring More Extensive Evaluation
Certain patient groups warrant broader laboratory screening 1, 3, 4:
- Age ≥65 years 1, 3, 4
- First psychiatric presentation (new-onset psychiatric symptoms) 1, 4
- Substance abuse history 1, 3
- Lower socioeconomic status 1, 3
- Patients with disorientation, altered cognition, or abnormal mental status 1
- Abnormal vital signs (fever, tachycardia) 1
- Preexisting or new medical complaints 1
- Evidence of self-neglect or organic mental disorders 3
- Immunosuppressed patients 4
Specific Tests with Limited Screening Value
Tests NOT Routinely Indicated:
- Urine drug screens: Sensitivity only 20% for organic etiology; does not alter disposition in most cases 1, 5
- Complete blood count (CBC): Not indicated routinely 3, 5
- Complete metabolic panel: Not indicated routinely 3, 5
- Electrocardiogram (ECG): Not indicated routinely except in psychogeriatric populations 1
- Chest radiograph: Not indicated routinely 1
- Electroencephalogram (EEG): Not indicated routinely 1, 3
- Erythrocyte sedimentation rate (ESR): Not indicated routinely 3
Tests with Selective Merit:
- Serum glucose, BUN, creatinine, and urinalysis: Have merit as broader screening tests in asymptomatic patients 3
- Thyroid function tests: Consider in patients with affective disorders, particularly women 1
- Vitamin B12 and folate: Higher deficiency rates in medically ill psychiatric patients; consider screening 6
- Urinalysis in women: May be considered 1
Critical Pitfalls to Avoid
- Do not order extensive screening batteries to "clear" psychiatric patients—this increases costs (estimated $36,325 in one study cohort) without improving outcomes 5
- Do not rely on laboratory tests alone—only 4% of psychiatric ED patients required acute medical treatment within 24 hours, and 83% of these cases were identifiable by history and physical examination 1
- Do not skip targeted history and physical examination—these are far more valuable than laboratory screening 2
- Beware of patients with altered vital signs or cognitive changes—these patients fall outside the "routine psychiatric patient" category and require medical evaluation for delirium and other organic causes 1
Patients on Psychotropic Medications
- Monitor for medication-specific side effects with appropriate laboratory tests based on the specific therapy being used 3