Multisite clinical evaluation of the iFAST rapid antimicrobial susceptibility test direct from positive blood cultures

Abstract

iFAST is a label-free rapid antimicrobial susceptibility test (AST) that delivers results in under 4 hours from a positive blood culture bottle. The technique measures changes in the electrical properties of thousands of individual bacteria following exposure to antibiotics. We report the diagnostic accuracy from the first clinical trial of the iFAST rapid AST system in three different labs according to ISO 20776-2:2021. Overall categorical agreement was 97.7% as compared to the reference laboratory broth microdilution method. iFAST specificity and sensitivity for the Enterobacterales was 98.2% and 96.6% respectively, and 96.9% and 98.4% for the non-fermenting Gram-negative bacteria, exceeding the acceptance criteria (≥95% sensitivity and specificity). Reproducibility was assessed with 12 isolates across 3 sites, in triplicate, on 3 separate days, with different operators at each site. Agreement was 95.7%.

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ORCID for Hywel Morgan: orcid.org/0000-0003-4850-5676

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