# Comparison of the VITEK REVEAL AST and Accelerate Pheno systems for fast antimicrobial susceptibility testing of gram-negative blood cultures at a large academic health system

## TL;DR

This study compares two rapid antimicrobial susceptibility testing systems for gram-negative blood cultures, finding high agreement and faster results with the VITEK REVEAL system.

## Contribution

The study evaluates and compares the performance of two FDA-cleared rapid AST systems directly from blood cultures, highlighting VITEK REVEAL's faster reporting and real-time MIC results.

## Key findings

- VITEK REVEAL and Accelerate Pheno showed 94.3% categorical agreement and 96.0% essential agreement for AST results.
- VITEK REVEAL reported antimicrobial susceptibility results significantly faster than Accelerate Pheno, with a mean final TTR of 7.9 h versus 7.1 h.
- VITEK REVEAL provides real-time MIC results, enabling earlier actionable information for antimicrobial stewardship.

## Abstract

Timely initiation of appropriate antimicrobial therapy is crucial for patients with Gram-negative (GN) blood stream infections. In this study, the performance of VITEK REVEAL (bioMérieux, USA), an FDA cleared in vitro diagnostic automated system for antimicrobial susceptibility testing (AST) directly from positive blood culture (BC), was compared to that of Accelerate Pheno (Accelerate Diagnostics, USA), as standard of care method. 128 GN positive BCs were analyzed according to manufacturer recommendations, comparing time to result (TTR) and AST results. The categorical agreement (CA) rate between VITEK REVEAL and Accelerate Pheno was 94.3% and the essential agreement (EA) rate was 96.0%. Very major discrepancies (VMD), major discrepancies (MD), and minor discrepancies (miD) rates between the systems were 7.5%, 0.5%, and 4.1%, respectively. Lastly, we observed a mean sequential TTR (reporting of AST results per antibiotic in real-time) on VITEK REVEAL of 6.1 h (3.0–8.2) and mean final TTR of 7.9 h (6.5–8.2), compared to Accelerate Pheno, with a significantly shorter mean final TTR of 7.1 h (6.8–7.7). Sequential TTR on VITEK REVEAL was significantly shorter for resistant isolates (those with ≥1 ‘Resistant’ antimicrobial-organism combination interpretation, using FDA STIC 2024 or CLSI M100 criteria) compared to susceptible/intermediate ones, with a mean difference of 1.4 h (P  <  0.001). Overall, compared to Accelerate Pheno, VITEK REVEAL displayed high %CA and %EA for AST of GN bacteria directly from positive BC. Also, unlike Accelerate Pheno, VITEK REVEAL reports MIC results in real time, allowing an earlier release of actionable information useful for antimicrobial stewardship.

Previous studies have compared the performance of the VITEK REVEAL, system for fast antimicrobial susceptibility testing (AST) to conventional, non-rapid microbiology methods. To evaluate how the VITEK REVEAL correlates to similarly available fast, direct-from-blood culture AST technologies, this study aimed to compare it to the Accelerate Pheno system, as standard of care method. High categorical agreement (94.3%) and essential agreement (96.0%) between the two systems were observed, underscoring their reliability. The VITEK REVEAL has the advantage of real-time AST reporting, unlike the Accelerate Pheno. Ultimately, this study supports the need for and continued optimization of fast diagnostic technologies for AST, contributing to the goal of advancing antimicrobial stewardship-focused treatment strategies and improving the prognosis of patients with bloodstream infections.