Laboratory Testing for Schizophrenic Patients with Polysubstance Use Disorder

Risk Stratification and Justification for Comprehensive Testing

Patients with polysubstance use disorder are at significant risk for organic causes of psychiatric symptoms, with 30% of new psychiatric presentations having toxicologic etiologies, according to the American College of Emergency Physicians 1
The combination of substance abuse history and schizophrenia creates a higher risk for metabolic derangements and medical complications, as noted by the American College of Emergency Physicians 2

A comprehensive metabolic panel should be performed to check for hyponatremia and other electrolyte imbalances that commonly occur with polysubstance use, as recommended by the American College of Emergency Physicians 1, 2
Serum glucose is essential as both hypoglycemia and hyperglycemia can mimic or exacerbate psychiatric symptoms, according to the American College of Emergency Physicians 1, 2
Renal function assessment is critical given potential nephrotoxicity from substances and to guide medication dosing, as noted by the American College of Emergency Physicians 2
TSH and free T4 should be performed as primary hypothyroidism can cause acute mania and psychiatric symptoms, according to the American College of Emergency Physicians 1
Urine toxicology screen should be performed to identify current substance use, assess for polysubstance use patterns, and guide treatment planning, as recommended by the American Academy of Family Physicians and the American College of Emergency Physicians 1, 3

Hepatic panel is appropriate given polysubstance use disorder and risk of hepatotoxicity from alcohol or other substances, as noted by the American Academy of Family Physicians 3

Routine extensive laboratory panels have extremely low yield (0.8-1.4%) when history and physical examination are normal, according to the American College of Emergency Physicians 1
Brain imaging is not indicated unless there are focal neurological deficits or history of head trauma, as recommended by the American College of Emergency Physicians 1
Lumbar puncture is only needed if CNS infection is suspected (fever, immunocompromised state), according to the American College of Emergency Physicians 1

History and physical examination can identify 94% of organic causes, making them more valuable than reflexive laboratory ordering, as noted by the American College of Emergency Physicians 1
The American College of Emergency Physicians recommends that diagnostic evaluation should be directed by history and physical examination rather than routine blanket testing 4
Do not assume psychiatric etiology without excluding medical causes in patients with substance abuse history and abnormal vital signs, as recommended by the American College of Emergency Physicians 2
Do not order reflexive extensive panels beyond what is clinically indicated by the specific risk factors present, according to the American College of Emergency Physicians and the American Academy of Family Physicians 1, 4