879. Host Response Classifiers Identify Infection and Illness Severity and Improve Antibiotic Decision-Making in Patients with Suspected Infections Presenting to the Emergency Department

BACKGROUND: Nonspecific presentation and limited diagnostic solutions of acute infections and sepsis in emergency departments (EDs) result in early antimicrobial administration at a cost to antimicrobial stewardship. We validated the host response classifiers, IMX-BVN-3b and SEV-3b, to determine bacterial and viral infection status and illness severity. We also assessed antibiotic over- and underuse. METHODS: We prospectively enrolled adult ED patients with suspected acute infections or sepsis with ≥1 vital sign abnormal across 7 sites. At enrollment, we surveyed treating physicians on infection probability and antibiotic prescribing. BVN/SEV-3b were calculated using NanoString nCounter® on PAXgene® blood samples. We compared BVN-3b likelihood of bacterial and viral infection to post-hoc clinical adjudication infection status and SEV-3b likelihood of severe outcomes to 7-day need for ICU care and 30-day mortality. RESULTS: Of 568 enrolled patients, 346 had consensus adjudications (131 bacterial, 52 viral, 1 coinfection, 162 noninfected). The BVN-3b area under the receiver operating curve (AUROC) for bacterial infections was 0.82 (95%CI 0.77-0.87), compared to 0.76 (95%CI 0.71-0.81) for procalcitonin (p = 0.011). BVN-3b AUROC for viral infections was 0.89 (95%CI 0.84-0.95). SEV-3b AUROC was 0.78 (95%CI 0.69-0.86) and 0.88 (95%CI 0.73-1) for 7-day ICU care and 30-day mortality, respectively. Of the 346, 226 patients had a pre-lab result physician questionnaire; of these, 110 patients received antibiotics. Of these, BVN-3b would have corrected 71% of antibiotic prescribing errors (34/48 overprescriptions and 13/18 underprescriptions). CONCLUSION: BVN-3b and SEV-3b accurately identified bacterial and viral infections and risk status. If implemented in a rapid workflow, these tests may improve patient management and antibiotic prescribing, reducing healthcare costs in the ED. DISCLOSURES: Arianna Beltran, BS, Inflammatix: Internship Uan-I Chen, MS, Inflammatix: Stocks/Bonds Edward A. Michelson, MD, Inflamatix: Research expense reimbursement for sponsored clinical trial Alexandra Weissman, MD, Inflammatix Inc: Advisor/Consultant Evangelos J. Giamarellos-Bourboulis, PhD, D(ABMM), Abbot Product Operations AG: Grant/Research Support|Abbot Product Operations AG: Honoraria|bioMerieux: Grant/Research Support|bioMerieux: Honoraria|Horizon 2020 European Program: Grant/Research Support|Horizon Health European Program: Grant/Research Support|Sobi AB: Advisor/Consultant|Sobi AB: Grant/Research Support|Sobi AB: Honoraria Oliver Liesenfeld, MD, Inflammatix Inc.: Ownership Interest Natalie N. Whitfield, PhD, D(ABMM), GenMark Dx/Roche: Employee|GenMark Dx/Roche: Stocks/Bonds|Inflammatix: Employee|Inflammatix: Stocks/Bonds