Impact of multiplex polymerase chain reaction testing in patients with bacteremia

Rapid identification of pathogens in bacteremia is critical for optimizing antimicrobial therapy. The FilmArray blood culture identification 2 (BCID2) panel enables multiplex PCR-based detection of pathogens and resistance genes. This study aimed to evaluate the clinical impact of BCID2 implementation in hospitalized patients with bacteremia. To this end, we conducted a retrospective study at a single Japanese center (May 2018-December 2024). The outcomes included length of stay, in-hospital mortality, antimicrobial days of therapy (DOT), and days of antimicrobial spectrum coverage (DASC) score. The pre-BCID2 and BCID2 implementation periods were compared. Among the 2,872 patients with positive blood cultures, BCID2 implementation was associated with a significant reduction in mortality (adjusted odds ratio [aOR] 0.58, 95% CI: 0.37-0.92, <i>P</i> = 0.021), specifically among those with bacteremia during weekday daytime hours when testing was available (aOR: 0.50, 95% CI: 0.28-0.89, <i>P</i> = 0.018). Age, sex, and intensive care unit (ICU)/high-care unit (HCU) admission were significant predictors of outcomes across all analyses. Implementing the BCID2 panel during weekday daytime hours within an active antimicrobial stewardship program (ASP) could significantly reduce mortality among patients with bacteremia when testing was available; however, it showed no benefits in the overall population. The findings of this study emphasize the importance of continuous availability and effective integration with ASP support to optimize clinical benefits. <b>IMPORTANCE</b> Rapid identification of the bacteria causing bloodstream infections is essential for timely and effective treatment. Traditional laboratory methods are often time-consuming, thus delaying therapy. Therefore, this study examined the application of the FilmArray blood culture identification panel, a rapid molecular test that can detect multiple pathogens and resistance genes within 1 h. We found that introducing this test during limited hours did not improve patient outcomes; rather, achieving optimal clinical impact may depend on continuous availability and effective collaboration with clinical decision-makers. This study emphasizes the need for unlimited access to rapid testing and support from stewardship programs to optimize clinical outcomes from this diagnostic technology in managing bloodstream infections.