The Impact of Fast Antimicrobial Sensitivity Testing Tools on Stewardship Antibiotic and Clinical Outcome (ACT-FAST)

The Impact of Fast Antimicrobial Sensitivity Testing Tools on Stewardship Antibiotic and Clinical Outcome: a Randomized Clinical Trial Within an Adaptive Platform Trial for Patients With Bloodstream Infections

The ACT-FAST study aims to compare commercially available Rapid Antimicrobial Susceptibility Testing (R-AST) tools with the current standard of care for patients with Bloodstream Infections (BSI). The primary objective is to evaluate whether "early targeted" antibiotic prescriptions, guided by these rapid tests, can improve antimicrobial stewardship and patient clinical outcomes.

To facilitate the evaluation of various diagnostic tools-including those currently on the market and those emerging in the near future-this study utilizes an adaptive clinical trial platform. This flexible design allows for the continuous assessment of different R-AST technologies within a single master protocol, ensuring that the most effective diagnostic strategies are identified efficiently.

ACT-FAST is a multicenter, open-label, randomized, adaptive clinical trial designed as the first domain of a broader adaptive platform. The study evaluates the clinical and stewardship impact of "early targeted" antibiotic therapy guided by Rapid Antimicrobial Susceptibility Testing (R-AST) compared to standard empirical therapy in patients with suspected bloodstream infections (BSI).

The study population consists of patients with positive blood cultures for whom pathogen identification and susceptibility results are still pending. Participants are randomized into one of two diagnostic strategies:

• Experimental Arm: Blood cultures are processed using R-AST testing tools to provide rapid phenotypic or genotypic susceptibility data.
• Standard of Care (SoC) Arm: Blood cultures are processed according to the standard laboratory diagnostic workflow of the participating center.

In both arms, results are communicated to the treating clinicians, who adjust antibiotic therapy based on their clinical judgment and routine practice. As an adaptive trial, the randomization ratios may be adjusted based on the number of active intervention arms. To ensure scientific rigor, outcome assessors remain blinded to the treatment allocation.

Patients are followed for a total of 28 days to assess clinical outcomes and antimicrobial stewardship objectives. The platform design allows for the integration of additional R-AST tools or interventions through future protocol amendments, ensuring the study remains at the forefront of diagnostic innovation.

Inclusion Criteria:

• Patients admitted to emergency department or hospitalized for any cause in participating hospitals with clinically suspected BSI and positive blood culture.
• At least 18 years of age.

Exclusion Criteria:

• Have previously taken part in this trial.
• Concurrently participating in the active phase of a study considered incompatible.
• Patient with severe or terminal disease with life expectancy shorter than 48 h.
• Have an existing directive to withhold life-sustaining treatment, in relation to antibiotic use.