Cheap Blood Test Can Discriminate Between Bacterial, Viral Infections

July 14, 2016

Breakthrough research from a Stanford University team brings doctors one step closer to the creation of a blood test that can determine whether infections are bacterial or viral, allowing doctors to make more informed decisions concerning antibiotic prescription (Science Translational Medicine. 2016;8(346):346ra91).

“The idea to look for a diagnostic test came from our previous paper…last year,” said assistant professor of medicine Purvesh Khatri, PhD, the senior author. “In that paper, we found a common response by the human immune system to multiple viruses that is distinct from that for bacterial infections. We wondered whether we could exploit that difference to improve the diagnosis of bacterial or viral infections.”

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The team conducted a multi-cohort analysis of publicly available gene-expression data to derive a set of 7 genes whose activity changes during an infection; the genes’ pattern of activity can distinguish whether an infection is bacterial or viral. They then validated the findings in 30 independent cohorts and used their previously published 11-gene Sepsis MetaScore together with the new bacterial/viral classifier to build an integrated antibiotics decision model.

In a pooled analysis of 1057 samples from 20 cohorts (excluding infants), the integrated antibiotics decision model had a sensitivity and specificity for bacterial infections of 94.0% and 59.8%, respectively (negative likelihood ratio 0.10).

To perfect the diagnosis process, the Stanford team is working with other researchers on a way to engineer the gene-expression test to provide results in less than an hour. The plan is to combine an 11-gene test the researchers created a few months ago with the more-recent 7-gene test. The 11-gene test would reveal whether a patient has an infection at all. If he or she does have an infection, the 7-gene test would then reveal whether it is bacterial or viral. Both tests would be run at the same time.

Researchers said the 18-gene combination test would first be used in hospitals. It’s possible that an even cheaper test just using the 7 genes could be used in outpatient clinics. —Amanda Del Signore