151. Comparing the Clinical Utility of Rapid Diagnostic Tests for Gram-Negative Bloodstream Infection Using a Desirability of Outcomes Ranking

BACKGROUND: Rapid diagnostic testing (RDT) technology in bloodstream infections (BSI) has outpaced provider understanding of how to effectively use it. To optimize the use of RDT platforms and antibiotic therapy, decision makers must determine which RDTs to implement at their institutions. A thorough understanding of which platform to choose extends beyond simple analytic measures of sensitivities and specificities and should include a robust analysis of how these RDTs could impact clinical decisions. METHODS: Retrospective study of adult patients with Gram-negative (GN) BSI from at University of Maryland Medical Center. The clinical microbiology laboratory used Verigene® BC-GN in clinical practice. Discarded blood samples were run on BioFire® FilmArray BCID. Final organism identification/susceptibility, antibiotic exposures, and clinical outcomes were reviewed. DOOR was applied to theoretical therapy decisions based on both actual prescribing adherence to institutional algorithm recommendations; 1 being most and 6 being least desirable (Table 1). A partial credit scoring system was applied to DOOR from most (100) to least desirable (0) outcome. Comparisons were made in a paired manner. RESULTS: 77 patients met inclusion. The median age was 58 (IQR 47, 68), 44.2% were in the ICU, and 75.3% had ID consult within 24 hours of BSI. Organism identification included: E. coli (35.1%), K. pneumoniae (23.4%), P. mirabilis (10.4%), S. marcescens (10.4%), Enterobacter spp. (9.4%), P. aeruginosa (3.9%). The only resistance determinant was CTX-M (11.6%). An antibiotic change occurred in 26.2% of cases, divided between antibiotic escalation and de-escalation. Based on the actual utilization of RDT results, median DOOR was not different between BC-GN and BCID (3 [IQR 3.4] vs. 4 [IQR 3.4], P = 0.44). Using a partial credit scoring system, the mean score was not different between platforms (49.8 [SD 26.8] vs. 47.7 [SD 20.3], P = 0.44). Through pairwise comparisons, BC-GN would have resulted in an optimal outcome of 15.3% (95% CI 4.7% to 19.3%) more often than BCID. CONCLUSION: Based on the actual use of RDTs for GN BSI there was no difference in potential clinical outcomes between platforms in this relatively small sample. DOOR is a novel mechanism to quantitate clinical utility and compare RDTs. [Image: see text] DISCLOSURES: All authors: No reported disclosures.