Effect of Direct-from-blood Bacterial Testing on Antibiotics Administration in Adults Presenting With Acute Infection

Vocabulary and key clinical trial concepts extracted from the randomized trial examining the effect of direct-from-blood bacterial testing on antibiotic duration.

T2Bacteria Panel

An FDA-cleared molecular diagnostic test (T2Biosystems) designed to detect five bacterial pathogens directly from whole blood: Staphylococcus aureus, Enterococcus faecium, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia coli.

Primary Outcome (Gaston et al. Trial)

The time between randomization and the start time of the last documented dose of intravenous vancomycin received by the patient within $14\,\text{days}$ of enrollment.

Secondary Outcome (Gaston et al. Trial)

The time between randomization and the start time of the last dose of systemic antipseudomonal beta-lactam antibiotic received by the patient within $14\,\text{days}$ of enrollment.

ePlex (Roche)

A rapid PCR platform performed on positive blood culture broth to identify bacteria and antimicrobial resistance genes.

Usual Care Group

The control group in the trial receiving standard blood cultures alone, finalized as no growth after a $5\text{-day}$ incubation period.

Time to Result for Direct-from-Blood Testing

A median duration of $7.9\,\text{hours}$ ($\text{IQR}, 7.0\text{--}10.0\,\text{hours}$) from randomization to available test results.

Concordance Rate

A $90.4\%$ ($188/208$ patients) rate of identical results observed between direct-from-blood testing and standard blood cultures in the intervention group.

Sensitivity of Direct-from-Blood Testing

$68.8\%$ compared to blood culture as the reference standard in the trial population.

Specificity of Direct-from-Blood Testing

$98.5\%$ compared to blood culture as the reference standard in the trial population.

Positive Predictive Value (PPV) of Direct-from-Blood Testing

$42.3\%$ compared to standard blood culture in the trial population.

Negative Predictive Value (NPV) of Direct-from-Blood Testing

$99.5\%$ compared to standard blood culture in the trial population.

Vancomycin Therapy Duration Result

Median time to last IV vancomycin dose was $12.5\,\text{hours}$ in the intervention group vs. $19.0\,\text{hours}$ in the usual care group ($\text{HR}, 1.08$; $95\%\,\text{CI}, 0.90\text{--}1.28$; $P = .42$), demonstrating no significant difference.

Antipseudomonal Beta-Lactam Therapy Duration Result

Median time to last systemic antipseudomonal beta-lactam dose was $1.6\,\text{days}$ in the intervention group vs. $1.7\,\text{days}$ in the usual care group ($\text{HR}, 1.04$; $95\%\,\text{CI}, 0.87\text{--}1.24$).

Neutropenia Subgroup Result

The prespecified subgroup (absolute neutrophil count $<1500\,\text{cells}/\mu\text{L}$) in which direct-from-blood testing appeared to shorten vancomycin duration (median $0\,\text{days}$ in intervention vs. $2\,\text{days}$ in usual care).

Trial Conclusion

Among adults with suspected infection receiving empiric IV vancomycin in the emergency department, use of direct-from-blood bacterial testing did not shorten the duration of IV vancomycin or antipseudomonal beta-lactam antibiotics.