Title : Incremental value of an ultra rapid phenotypic antimicrobial susceptibility testing in patients with bloodstream infection: A modeling approach
Abstract:
Background and Goal: When bloodstream infection (BSI) is suspected, empirical broad-spectrum antimicrobial treatment (AMT) is immediately initiated after sampling for blood cultures. In the context of an increasing rate of multidrug-resistant organisms, rapid microbiological investigations—identification of the causative agent and antimicrobial susceptibility testing (AST) – are key to minimize time on inappropriate therapy, to limit the selection of resistant strains and to limit AMT-associated toxicity. This study aimed to quantify the health and economic gains achievable by replacing the current standard of care (SoC) with an ultra-rapid AST directly performed from blood cultures.
Methods: A decision-tree model was developed to compare between SoC (isolation in culture medium + MALDI-TOF-MS + VITEK 2 AST), which has a time to results (TTR) of 51 hours(h), rapid ASTs (5h<TTR<8h), and FASTinov ultra-rapid (UR) AST (TTR=2h), in hospitalized patients with BSI. Outcomes of interest were mortality, hospital length of stay (LoS) and costs. Outcomes were linked to TTR through the duration of inappropriate therapy. Inputs were based on the literature. Conservatively, due to lack of evidence, AST TTR was assumed not to impact outcomes in patients initiating appropriate empirical therapy. A time-horizon of 30 days was considered, and the payer perspective was adopted.
Results: The 2h TTR UR-AST test allows for decision-making in the same medical shift, while rapid ASTs likely yield next day intervention, and SoC requires at least 3 days to achieve AST based optimized regimen. In that context, in the overall BSI patient population, replacing current SoC with FASTinov UR-AST allows reductions of 8.0% in mortality (12.4% vs 13.5%), 30.1% in LoS (6.7 vs 9.6 days) and 28.0% in costs (6,148€ vs 8,542€)When comparing the 2h TTR UR-AST to rapid ASTs, the benefit is estimated to result in a reduction of 8.0% in mortality, 15.7% in LoS (6.7 vs 7.9 days) and 14.3% in costs (6,148€ vs 7,177€)..
Conclusion: Availability of AST results on the same medical shift reduces mortality, LoS and costs of hospitalized patients with BSI.
