The Yield of One vs. Two Blood Cultures in Children: Under-Detection and Over-Testing

Area of Science:

• Medical Microbiology
• Infectious Diseases
• Pediatric Healthcare

Background:

• Bloodstream infections (BSIs) are a critical concern in pediatric populations.
• Current diagnostic practices often rely on single blood cultures (BCs).
• The sensitivity and specificity of single BCs for detecting BSIs in children require further investigation.

Purpose of the Study:

• To evaluate the impact of collecting two BCs versus one on the detection rates of BSIs in pediatric patients.
• To determine the additional diagnostic yield of a second BC in identifying true pathogens.
• To assess the rate of contamination and differentiate it from true BSI in pediatric blood cultures.

Main Methods:

• A descriptive study utilizing surveillance data from Israeli pediatric hospitals between 2019 and 2021.
• Analysis of 178,702 blood culturing episodes, comparing outcomes from single versus paired BC collections.
• Statistical comparison of pathogen detection rates and identification of contaminants between single and two-BC strategies.

Main Results:

• Two BCs detected true pathogens in 8.9% of episodes, compared to 1.0% with a single BC (p < 0.001).
• The second BC alone identified a true pathogen in 16.0% of positive paired cultures.
• An estimated 343 additional BSIs could be detected annually with universal two-BC protocols.
• Single BCs had a high rate of commensal bacteria (64.7%), complicating BSI diagnosis due to potential contamination.

Conclusions:

• Collecting two blood cultures significantly enhances the detection of bloodstream infections in children.
• A single blood culture strategy is associated with lower sensitivity and a higher proportion of ambiguous results due to commensal organisms.
• Implementing routine two-BC collections is recommended to improve pediatric BSI diagnosis and patient management.