2168. Comparison of Rapid Diagnostic Tests for Bloodstream Infections Using Desirability of Outcome Ranking Management of Antimicrobial Therapy (DOOR-MAT)

BACKGROUND: Rapid diagnostic tests (RDTs) for bloodstream infection (BSIs) are increasingly common. Decisions regarding which RDT to implement remains a clinical challenge given the diversity of organisms and resistance mechanisms detected by different platforms. The desirability of Outcome Ranking Management of Antimicrobial Therapy (DOOR-MAT) has been proposed as a framework to compare RDT platforms but reports of clinical application are lacking. This study compared potential antibiotic decisions based on results of two different RDTs for BSI using DOOR-MAT. METHODS: Retrospective study at University of Maryland Medical Center from August 2018 to April 2019 comparing Verigene® BC (VBC) to GenMark Dx ePlex® BCID for clinical blood cultures. VBC was part of standard of care, ePlex was run on discarded fresh or frozen blood samples. In this theoretical analysis, RDT result and local susceptibility data were applied by two Infectious Diseases pharmacists to make decisions regarding antibiotic selection in a blinded manner. Cohen’s Kappa statistic summarized overall agreement. DOOR-MAT, a partial credit scoring system, was applied to decisions based on final organism/susceptibility results (Figure 1). Scores were averaged between reviewers and mean scores compared between RDT systems using the t-test. Additionally, a sensitivity analysis with varied point assignment among Gram-negatives (AmpC-producers) was conducted. RESULTS: 110 clinical isolates were included; 41 Gram-negative, 69 Gram-positive organisms. Overall agreement was 82% for VBC and 83% for ePlex. The average score for VBC was 86.1 (SD 31.3) compared with ePlex 92.9 (SD 22.9), P = 0.004. Among Gram-negatives, the average score for VBC was 79.9 (SD 32.1) compared with ePlex 88.1 (SD 28.8), P = 0.032. Among GPs the average score for VBC was 89.9 (SD 30.4) compared with ePlex 95.8 (SD 18.3), P = 0.048. Sensitivity analysis demonstrated an average score for of 89.9 (SD 30.4) for VBC compared with 95.8 (SD 18.3) for ePlex, P = 0.27. CONCLUSION: The use of a partial credit scoring system such as the DOOR-MAT allows for comparisons between RDT systems beyond sensitivity and specificity allowing for enhanced clinical interpretation. In this theoretical comparison, the Genmark ePlex BCID scored higher among both GP and GN organisms. [Image: see text] DISCLOSURES: All authors: No reported disclosures.