What laboratory tests are recommended for a patient presenting with psychomotor agitation?

Laboratory Work-Up for Psychomotor Agitation

In alert, cooperative patients with psychomotor agitation who have normal vital signs and a noncontributory history and physical examination, routine laboratory testing is not indicated—diagnostic evaluation should be directed by clinical findings from the history and physical examination. 1

Clinical Assessment Determines Testing Strategy

The American College of Emergency Physicians establishes that selective, targeted laboratory testing based on clinical suspicion is the appropriate approach rather than reflexive ordering of comprehensive panels. 1 This recommendation stems from evidence showing that history and physical examination identify 83-98% of clinically significant abnormalities, while routine testing yields true positive results in only 1.8% of cases—with false positives occurring 8 times more frequently. 1

High-Risk Populations Requiring Lower Testing Threshold

Certain patient groups warrant more extensive evaluation regardless of initial presentation: 1, 2

• Elderly patients (consider electrolytes, thyroid function, vitamin B12) 1, 2
• First psychiatric presentation (broader metabolic workup indicated) 1, 2
• Substance abuse history (toxicology screening appropriate) 1, 3
• Lower socioeconomic status (increased risk of undiagnosed medical illness) 1
• Patients with new medical complaints (targeted testing for specific concerns) 1

Red Flags Mandating Immediate Laboratory Evaluation

Any deviation from the "alert, cooperative, normal vital signs" profile requires targeted testing: 2

• Altered mental status, disorientation, or confusion suggests delirium and necessitates comprehensive metabolic panel, complete blood count, and consideration of additional testing 2
• Fever mandates complete blood count, blood cultures, and infection workup 2
• Vital sign abnormalities (tachycardia, hypertension, hypotension) require electrolytes and targeted evaluation for underlying cause 2
• Focal neurological deficits necessitate neuroimaging and broader evaluation 2

Specific Laboratory Tests When Clinically Indicated

Metabolic Testing

• Serum glucose: Check when hypoglycemia or hyperglycemia suspected based on history or examination 2
• Serum sodium: Order when medication use (diuretics, SSRIs), excessive water intake, or clinical signs suggest electrolyte disturbance 2
• Basic metabolic panel: Warranted in patients with known renal disease, medications affecting electrolytes, or signs of metabolic derangement 2

Thyroid Function

• Thyroid-stimulating hormone: Consider in elderly patients with affective disorders or when clinical features suggest thyroid dysfunction 1, 4
• Subacute thyroiditis can present as acute psychosis with psychomotor agitation, particularly in younger patients with abrupt symptom onset 4

Toxicology Screening

• Urine drug screen: Appropriate in pediatric/adolescent patients given high substance abuse rates 1
• In adults, toxicology screening should be guided by clinical suspicion rather than routine practice 1
• Benzodiazepines and alcohol are the most common substances found in agitated patients, often in combination 3

Additional Testing in Geriatric Patients

• Vitamin B12 and folate: Consider in older adults with cognitive changes 2
• Medication review: Critical given polypharmacy commonly causes agitation in this population 2

Critical Pitfalls to Avoid

Do not order extensive routine laboratory panels reflexively—this approach has very low yield (1.8% true positives) and generates false positives that lead to unnecessary interventions and delays in appropriate psychiatric care. 1, 2

Never assume psychiatric etiology without excluding medical causes in high-risk groups—elderly patients, first presentations, those with abnormal vital signs, or substance abuse history require thorough medical evaluation before attributing symptoms to primary psychiatric illness. 1, 2

Do not overlook serotonin syndrome—this diagnosis is frequently missed in agitated patients taking selective serotonin reuptake inhibitors, particularly when combined with other serotonergic agents. 3

Pediatric Considerations

In children and adolescents presenting with psychomotor agitation, the American Academy of Child and Adolescent Psychiatry recommends comprehensive medical evaluation to exclude organic causes when psychotic symptoms or severe agitation are present. 1 However, similar to adults, routine testing in the absence of clinical indicators does not alter management—only 3 patients out of 208 in one study had laboratory abnormalities requiring intervention, all of which were suspected based on history and examination. 1