Genetic test detects infections before symptoms appear

By Steve Sternberg, USA TODAY
8/6/2009

Flu sufferers of the future may not have to wait until their fever spikes to learn they're ill, scientists said Thursday.
Geoffrey Ginsburg of Duke University and his colleagues say that they've developed an experimental genetic test that can detect infections before any symptoms appear.
Although the test cannot yet distinguish one virus from another, it can tell the difference between a bacterial and a viral illness, Ginsburg says.
Most diagnostic tests detect the germ itself or antibodies produced by the immune system to wipe out a virus or bacteria once the symptoms begin. The new approach works differently, by detecting genetic signs of infection in people who aren't sick yet.
The test betrays the activation of genes that govern an immune response. It is carried out using a silicon chip much like those used in computers and requires no more than the 10 microliters of blood from a finger-prick.
"This is the first major step in using a person's individual response to a viral or bacterial infection to lead to better diagnostics for infectious disease," Ginsburg says.
The goal of the research, sponsored by the U.S. military's Defense Advanced Research Projects Agency (DARPA), is to develop a device that can identify troops who are getting sick, in time to get them treated and to prevent them from infecting others. Ultimately, Ginsberg says, the method could also become a valuable diagnostic tool in emergency rooms and doctors' offices, where a simple test could tell the difference between the worried well and the genuinely sick.
"The true market for this may be in doctors' offices around the world, where kids are coming in with fevers and doctors have to make decisions about giving them an antibiotic," he says, noting that antibiotics can be expensive, have side effects and promote the spread of drug-resistant germs.
Arnold Monto, of the University of Michigan School of Public Health, says a test that could accurately identify viral illness, especially influenza, would be a critically important advance. "A chip like this would be great," Monto says. Not only would it help doctors more accurately diagnose people who are ill, but it would also provide public health officials with information critical to their efforts to fight epidemics.
The accuracy of the rapid tests that are currently available is inconsistent, ranging from 30% to 80%, and prompting public health officials to caution against their use. An accurate genetic test would serve multiple purposes, Monto says.
"If we could identify people before they get sick — say, in household studies — we could get a better idea of how the virus is transmitting," he says. "How influenza is transmitted affects (predictions of an epidemic's spread), control measures and personal protective measures," shedding light on how best to keep from getting infected.
Ginsburg and his team tried out the method in volunteers they infected with cold viruses, flu viruses and a less well-known cause of upper airway disease called respiratory syncytial virus. The study appears today in the journal Cell, Host & Microbe.
The study involved 57 volunteers. Their blood was drawn before and after they were infected so that each one could serve as a healthy control.
Researchers were able to tell the difference someone who was infected and someone who wasn't with 95% accuracy. The test could also distinguish between people who were infected with viruses and those with bacteria more than 93% of the time.
The researchers are trying to determine whether the test will work in patients infected with H1N1, or swine, flu.