Cultures after 24 hours of fever unlikely to detect new bloodstream infections

MEMPHIS, Tenn. — While repeat blood cultures are vital to diagnosing new bloodstream infections and guiding antibiotic therapy in children who present with fever and neutropenia, after the first 24 hours of fever, the likelihood of identifying a new bloodstream infection is significantly reduced.

According to Rachel L. Wattier, MD, MHS, of the University of California San Francisco, and colleagues, the clinical impact that repeat blood cultures from children with persistent fever and neutropenia have on individual patient management remains uncertain. Wattier presented data at the St. Jude/PIDS Pediatric Infectious Diseases Research Conference.

To determine the value of daily blood cultures in high-risk children with persistent fever and neutropenia, Wattier and colleagues reviewed blood culture results from children (n = 135) undergoing treatment for hematologic malignancy or stem cell transplantation from July 2006 to June 2012.

Researchers identified 184 episodes of persistent fever and neutropenia in these patients, during which 17 new bloodstream infections were diagnosed after the initial 24 hours of fever (9.2%; 95% CI, 5.4%-15.3%).

For each persistent fever and neutropenia episode, the researchers examined blood culture results to assess the yield of true-positive and false-positive results by day of collection. In addition, they studied culture-level and episode-level predictors to evaluate factors linked to new bloodstream infection diagnosis.

After the first 24 hours, the rate of new bloodstream infection was 1.5% (95% CI, 1%-2.4%) per day, and the rate of blood culture contamination was 1.1% (95% CI, 0.6%-2.1%).

Of the new bloodstream infections identified, the researchers said 14 required a change in antibiotic therapy, whereas all of the contaminant blood cultures were followed by additional antibiotic therapy.

“For children with persistent fever and neutropenia, repeat blood cultures are helpful in identifying new bloodstream infections in a small portion of cases, and the new bloodstream infections that occur in these cases are likely to require changes in management,” Wattier told Infectious Diseases in Children. “However, after the first 24 hours of fever, the chance of identifying a new bloodstream infection on any given day is low, and is similar to the chance of a false-positive blood culture.”

In addition, the researchers observed that increased odds of new bloodstream infection diagnoses were associated with a history of bloodstream infection within 30 days of the episode (OR = 5.18; 95% CI, 1.29-20.8) as well as increasing breaks between recurrent fevers (OR = 1.29; 95% CI, 1.06-1.57).

“We identified two predictors that were associated with new bloodstream infections after the first 24 hours, enabling risk stratification,” Wattier said. “We hope that these results prompt clinicians to consider reducing the frequency of repeat blood cultures in children with fever and neutropenia, particularly those with lower risk features.” – by Bob Stott

Reference:

Wattier RL, et al. Abstract R201510. Presented at: St. Jude/PIDS Pediatric Infectious Diseases Research Conference; Feb. 20-21, 2015; Memphis, Tennessee.

Disclosure: The researchers report no relevant financial disclosures.