Episode 100: Autoimmune encephalitis testing with Tammy Smith

In this episode of Critical Care Scenarios, hosts Brandon Odo and Brian Bowling dive deep into the complex world of autoimmune encephalitis testing with Dr. Tammy Smith, an assistant professor of neurology and clinical consultant at Arup Laboratories. The discussion centers on the challenges clinicians face when diagnosing autoimmune encephalitis—a condition often presenting with subtle, non-specific symptoms like behavioral changes, confusion, seizures, and altered consciousness. Dr. Smith explains that while the disease spectrum is rare, testing is frequently ordered in a broad, shotgun fashion due to diagnostic uncertainty. She emphasizes the importance of selecting the right antibody panel based on clinical phenotype (e.g., encephalitis, epilepsy, or movement disorders), sending samples from both serum and CSF, and understanding that results can be influenced by prior treatments like IVIG or plasma exchange. The episode highlights that most panels return negative, and that clinical context—especially response to first-line immunotherapy—is often more telling than lab results alone. Dr. Smith also stresses the value of consulting specialists, using reference lab support services, and avoiding over-testing, particularly when results may lead to false positives or unnecessary interventions. Key takeaways include: (1) Always consider autoimmune encephalitis in patients with subacute neurological decline, especially with behavioral changes or refractory seizures; (2) Order the most appropriate panel based on clinical presentation, not just a broad 'one ring to rule them all' test; (3) Send both serum and CSF samples, as serum may detect antibodies missed in CSF; (4) Be cautious with results after IVIG or plasma exchange, which can cause false positives or reduce sensitivity; (5) A negative panel doesn’t rule out disease—clinical response to immunotherapy is critical; (6) Use the Grouse criteria for antibody-negative autoimmune encephalitis; (7) Don’t hesitate to consult specialists or reference lab experts; and (8) Early, targeted immunotherapy (steroids, IVIG, or plasma exchange) should be initiated empirically while awaiting results. The overall tone is cautiously optimistic, emphasizing that while the field is complex and evolving, clinicians can make meaningful progress with thoughtful, framework-based decision-making.