What: Rapid antimicrobial susceptibility tests (rASTs) are in vitro diagnostic tests for determining the susceptibility of bacterial or fungal isolates to antimicrobial agents. Unlike conventional phenotypic, antimicrobial susceptibility test (AST) methods that require lengthy incubation periods for culture, rASTs are intended to provide quick results. Many have the stated goal of providing “same day susceptibility” results. Rather than being used for all specimens and isolates, rASTs are generally implemented on a sub-set, and rAST direct from blood culture is a common target.
Who: Non-proprietary rAST methods have been developed and standardised by breakpoint-setting agencies EUCAST and CLSI. There are also commercially available rAST systems. Both non-proprietary and commercial systems are in clinical use, with increasing adoption. Several commercial systems are in development.
Where and When: Rapid phenotypic ASTs are typically used in mid-tier-complexity clinical laboratories and higher. Their use is usually reserved for samples from time critical infections such as bloodstream infections. Adoption of commercial rAST systems is heavily influenced by performance, cost and regulatory marketing approval.
Why: Increasing AMR undermines empirical treatment choices and leads to delays in patients receiving effective antimicrobial therapy which is known to contribute to mortality. Impacts on antimicrobial stewardship are also considerations. Adoption of rASTs is influenced by many factors including a) the availability of evidence showing new rapid tests meet stringent performance specifications, b) endorsement by peak bodies c) approval from regulatory agencies and d) evidence of clinical impact.
These factors and the range of rASTs being developed or already in the market will be reviewed. By examining their various merits and limitations, we can better understand what opportunities and challenges exist for rASTs.