1821. Evaluation of Cerebrospinal Fluid White Blood Cell Count Criteria for Use of the BioFire(®) FilmArray(®) Meningitis/Encephalitis Panel in Immunocompetent Patients

BACKGROUND: In 2016, our academic medical center implemented the BioFire(®) FilmArray(®) Meningitis/Encephalitis Panel (MEP), which detects 14 viral, bacterial, and fungal pathogens. Institutional guidelines recommended the test be used in nonimmunocompromised patients age ≥2 years only if the cerebrospinal fluid (CSF) white blood cell (WBC) count was >10 cells/mm(3). METHODS: We reviewed all MEP performed at our institution over 2 years (January 1, 2017 to December 31, 2018). We collected CSF WBC count, protein, and glucose; MEP results; CSF culture results; and demographics. We excluded children age <2 years, immunocompromised patients, those without a CSF WBC count, and duplicate tests during the same illness. RESULTS: Of 453 patients, 311 met inclusion criteria. The median age was 51, 51% male. Median CSF indices: WBC/mm(3) = 4, protein = 57 mg/dL, glucose = 66 mg/dL. MEP positivity rate = 12% (37/311): viruses (29/37), bacteria (7/37), and fungi (1/37). Positive bacterial/fungal MEP results compared with CSF culture are summarized in Table 1. No clinically significant discordant negative MEP results occurred compared with CSF culture, cryptococcal antigen, or other viral PCR testing. Of the 311 patients, 184 (59%) had ≤10 CSF WBC/mm(3). Of these, 4 had positive MEP results: 1 enterovirus, 1 human herpes virus 6 (HHV-6) and 2 varicella zoster virus (VZV). The HHV-6 was judged clinically insignificant. The 2 VZV cases had concomitant shingles and were already on acyclovir. No clinically significant MEP results occurred in 110/311 (35%) patients with ≤ 2 CSF WBC/mm(3). CONCLUSION: In nonimmunocompromised patients, age ≥ 2, with ≤ 10 CSF WBC/mm(3) on lumbar puncture, positive MEP results were rare and the clinical significance of the 4 positives was debatable. A hard-stop restriction in this setting could have reduced overall use by up to 59% and resulted in significant cost savings. Lower CSF WBC/mm(3) cut-offs could be considered and still improve MEP utilization. [Image: see text] DISCLOSURES: All Authors: No reported Disclosures.