Rapid Blood Infection Test Fails To Improve Survival

Key Takeaways

• Rapid testing was not superior to standard susceptibility testing for 30-day clinical outcomes, including mortality, in gram-negative bloodstream infection.
• Faster overall antibiotic escalation or de-escalation was observed, along with more timely antibiotic modification, targeted therapy in some subsets, and greater acceptance of stewardship recommendations.
• Both groups received antimicrobial stewardship review, the rapid panel did not cover all organisms, and local treatment access or resistance conditions may affect how these findings apply elsewhere.

Rapid antimicrobial susceptibility testing directly from positive blood cultures produced results in about 7.5 hours, compared with 44 hours with standard testing, in a randomized gram-negative bloodstream infection trial. Yet it was not superior to standard susceptibility testing for 30-day clinical outcomes in gram-negative bloodstream infection. Mortality and other broader 30-day measures were unchanged despite the faster laboratory turnaround.

The open-label randomized trial assigned 899 patients, with 850 included in the primary analysis. The study was conducted at seven medical centers across four countries with a high prevalence of antimicrobial resistance. The intervention used rapid susceptibility testing directly from positive blood culture bottles in addition to standard testing, while the comparator relied on standard testing performed on subcultured bacteria. Antimicrobial stewardship teams reviewed both groups and provided recommendations, with the main clinical assessment set at day 30. The comparison therefore paired faster direct testing with the conventional workflow under shared stewardship support.

No significant differences were seen in 30-day mortality, hospital stay, ICU admission, hospital-acquired infections, or time to effective antibiotic therapy within three days. There was also no significant difference in time to antibiotic escalation or de-escalation within three days. Nearly two-thirds of patients in both groups were already receiving effective antibiotic therapy at enrollment. Even so, the rapid-testing group had faster antibiotic escalation or de-escalation overall. Those process gains remained separate from the unchanged main clinical outcomes.

About one-fifth of patients had organisms not included on the rapid testing panel, which could have reduced the intervention's reach. The trial did not evaluate the independent effect of rapid testing apart from stewardship review and did not assess cost-effectiveness. Investigators also noted associations with timelier antibiotic modifications, targeted therapy in certain subsets, and greater acceptance of stewardship recommendations. In carbapenem-resistant infections, rapid testing was associated with fewer patients remaining hospitalized at day 30 rather than a clear overall length-of-stay benefit. How these findings apply elsewhere may vary with institution, patient complexity, susceptibility methods, pathogen prevalence, resistance patterns, and local access to the most effective therapies.