New blood test can quickly reveal whether a child has a bacterial infection. If the test, described in the March Journal of Pediatrics , can be developed for widespread use, it could help doctors save the lives of some infants, as well as millions of dollars in treatments for babies appear to have infections.
Because infants are so vulnerable to infections, doctors must make hasty decisions as to whether a baby who looks ill really needs an antibiotic. Often wandering on the safe side, the doctors end up treating 17 healthy babies for everyone who is later confirmed to have an infection. For a decade, immunologists have sought a molecule in the immune system of the newborn which could serve as a warning flag for an infection. But the molecules tested so far, none have been proven.
Leonore Herzenberg, Erica Weirich, and their colleagues at Stanford University Medical Center has undertaken to develop a simple blood test for the latest and most promising sentinel molecule called CD11b. The molecule appears on the surface of neutrophils, a type of immune cell, within 5 minutes of being exposed to a bacterial toxin called saccharide lipopoly. Researchers designed a fluorescent marker that clings to CD11b and can be accessed regularly by Laserlight. They screened blood of 106 children suspected of having an infection, or high risk for one. They also come with a proven, but slower test for an infection that flags C-reactive protein (CRP). Every 15 babies tested positive for CRP, which is produced in large quantities during infection, were also positive for CD11b. In addition, there were no false positive results CD11b.
If confirmed, the results "could ultimately change how doctors decide how to treat newborns," said Herzenberg. But Robert Baltimore, a pediatrician at Yale University Children Hospital, is not so sure. Although the test "has a very high predictive value", he said, he could suffer the fate of many previous laboratory tests for babies - doctors ignore. "Very often, they will order the test and treat babies anyway," even if the test comes out negative, he said.
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