Cell-free DNA offers early warning for bloodstream infections in kids with leukemia

Researchers show microbial cell-free DNA sequencing can predict infections days before symptoms appear, allowing earlier treatment.

Published on Mar. 2, 2026

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Researchers at St. Jude Children's Research Hospital have identified a promising way to predict bloodstream infections in children with high-risk leukemia days before the infection would be diagnosed using current standards of care. The test, named plasma microbial cell-free DNA sequencing (mcfDNA-Seq), detected infection-causing pathogens days before standard blood cultures, offering a potential approach to protecting vulnerable patients by allowing treatment to start before the patient gets sick.

Why it matters

Bloodstream infections are a major threat to children undergoing treatment for leukemia, as chemotherapy weakens the immune system. Catching these infections early is critical, yet clinicians currently have no reliable method to identify infections before symptoms appear. The new mcfDNA-Seq test could allow for earlier treatment and improved outcomes for these vulnerable patients.

The details

In this prospective study, researchers analyzed plasma samples collected daily from 158 pediatric patients with high-risk leukemia. They selected samples from up to seven days before and at diagnosis of a bloodstream infection and tested them using mcfDNA-Seq, a technology that detects fragments of microbial DNA circulating in the blood. mcfDNA-seq predicted bloodstream infections in just over half of cases up to three days before symptoms appeared. The test reliably identified the most common bacteria and fungi that cause bloodstream infections in children with cancer, while accurately ruling out infection in 93.8% of samples from healthy or uninfected patients.

  • The study was published today in The Lancet Microbe.

The players

Joshua Wolf

PhD, MBBS, first and corresponding author of the study, St. Jude Department of Infectious Diseases.

St. Jude Children's Research Hospital

A leading pediatric research hospital dedicated to advancing cures and means of prevention for childhood catastrophic diseases through groundbreaking research and compassionate care.

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What they’re saying

“We're not good at predicting or preventing infections in children with cancer, and the consequences can be deadly, causing lasting damage or delaying chemotherapy, which reduces the chances of successful treatment. Many infections still happen even with the best prevention strategies we have, so what we really need is a way to detect infections before they start, so we can treat kids earlier and save lives.”

— Joshua Wolf, PhD, MBBS, first and corresponding author of the study, St. Jude Department of Infectious Diseases (The Lancet Microbe)

“The data can indicate when a patient is likely to get sick. The challenge now is figuring out how to act on that information effectively.”

— Joshua Wolf, PhD, MBBS, first and corresponding author of the study, St. Jude Department of Infectious Diseases (The Lancet Microbe)

What’s next

Further clinical trials are needed to evaluate how best to incorporate this mcfDNA-Seq approach in treatment decisions for high-risk pediatric cancer patients.

The takeaway

This new mcfDNA-Seq test represents a promising advancement in the fight against life-threatening bloodstream infections in children with leukemia, offering the potential to detect infections days before symptoms appear and allow for earlier, more effective treatment to improve outcomes for these vulnerable patients.