Performance Verification of the Accelerate Pheno™ System for Rapid Identification and Antimicrobial Susceptibility Testing from Positive Blood Culture in a Pediatric Population

BACKGROUND: Early targeted antibiotic therapy is crucial when treating pediatric patients with bacteremia. While identification (ID) and antimicrobial susceptibility testing (AST) of bloodstream pathogens are critical to optimizing therapy, conventional methods can take days resulting in inappropriate use of broad-spectrum antibiotics. The automated Accelerate Pheno™ system (AXDX) provides ID in <90 minutes and AST in <7 hours directly from positive blood culture (PBC), enabling clinicians to optimize antibiotic therapy sooner to improve patient outcomes. In addition, the unique AXDX Monomicrobial call effectively rules out polymicrobial samples by indicating only one bacteria is present in the PBC. This study verifies AXDX performance compared with current laboratory ID and AST methods. METHODS: A total of 54 pediatric PBC (33 spiked, 21 fresh) were tested within 8 hours of positivity (30 Gram-positive, 20 Gram-negative, 2 yeast, 2 off-panel species). A 0.5 mL aliquot was placed in an Accelerate PhenoTest™ BC kit sample vial and run on AXDX. Current laboratory methods for ID (Biofire Filmarray BCID, VITEK® 2, or MALDI-TOF) and AST (VITEK® 2 or Microscan) were run in parallel as comparators. Sensitivity (SN) and specificity (SP) were calculated for ID and essential (EA) and/or categorical agreement (CA), major (ME) and very major errors (VME) for AST. Positive predictive value (PPV) for the Monomicrobial call in fresh samples was calculated. RESULTS: Three samples were excluded (1 technical and 2 ID failures) and a total of 51 PBC samples were evaluated and analyzed. Following adjudication of discrepant results, AXDX demonstrated 100% SN and SP, with 97.7% EA and 96.8% CA compared with current laboratory methods. The single VME and 2 of 3 ME were adjudicated to AXDX. The two off-panel organisms did not result in ID or AST from AXDX. The PPV for the Monomicrobial call was 100%. Overall times to ID and AST were reduced by 18.5 hours and 31.2 hours, respectively. CONCLUSION: The Accelerate Pheno™ system demonstrated high performance for both ID and AST of PBC much faster than current laboratory methods. Implementing this system will allow laboratories to provide clinicians with actionable results much sooner, enabling them to optimize therapy earlier to improve patient outcomes. DISCLOSURES: A. J. Blaschke, BioFire Diagnostics LLC: Collaborator, Have intellectual property in BioFire Diagnostics through the University of Utah and Investigator, Licensing agreement or royalty and Research support