347. Etiologies in a Cohort of Pediatric Patients Who Underwent CSF Metagenomic Next Generation Sequencing

BACKGROUND: The differential diagnosis in pediatric patients presenting with concern for CNS infections and/or autoimmune disorders is broad. Despite recent advances in diagnostic modalities, many cases may remain undiagnosed. For example, approximately 50% of pediatric patients with encephalitis do not have an identified etiology. Use of metagenomic next-generation sequencing (mNGS) may improve the diagnostic yield. This study evaluated etiologies in a cohort of pediatric patients who underwent CSF mNGS. METHODS: Retrospective cohort study of all hospitalized patients < 21-years-old who underwent CSF mNGS at a tertiary pediatric hospital from June, 2017 - February, 2020. Final diagnosis was assigned by two independent study physician reviewers (pediatric infectious disease and neurologist) based on documentation including discharge summaries, consult notes, and subsequent clinic notes where available. RESULTS: Thirty-seven patients (59% female, median age 9 (1–17) years) were identified (21 with encephalitis). Twenty-six (70%) had a definite diagnosis – 10 (27%) infectious, 11 (30%) autoimmune, 5 (14%) other. The most common etiology was anti-MOG antibody associated meningoencephalitis (n=4, 11%). Among infections, Powassan virus encephalitis (n=3, 8%) was most common; other infectious etiologies included EBV, neuroborreliosis, rubella, and Eastern Equine encephalitis. Eight (22%) had a positive result on CSF mNGS; 7 were clinically significant including change in management in 5 of 8 (63%) patients. CONCLUSION: In this cohort of pediatric patients who underwent CSF mNGS, an etiology was identified in 70%. Eight patients had a positive result on mNGS which resulted in change in management for the majority of patients. These data suggest that CSF mNGS is high-yield and impacts clinical care. However, given the significant cost of mNGS, future directions include cost analyses to determine when and in whom CSF mNGS should be sent. DISCLOSURES: Asim A. Ahmed, MD, Karius (Employee)