Anyone who has ever watched the television show House knows that you have to be an eccentric super genius to diagnose rare illnesses. You have to figure out which one-in-a-million virus or bacteria may be causing a host of bizarre symptoms, and then you test for it. And you have to go through this on average 3.2 times per patient to finally get positive test results, allowing time for lots of telegenic hijinks along the way.
But a new test developed at Washington University School of Medicine in St. Louis and funded by the National Institutes of Health (NIH) may be putting Dr. House out of a job. It can detect virtually any virus that infects people and animals, all in one fell swoop.
Even outside of television-land, making a diagnosis really can be a taxing exercise. Current diagnostic technology isn’t sensitive enough to detect low levels of viruses or are limited to testing specifically for a suspected illness, notes researchers.
"With this test, you don't have to know what you're looking for," says the study's senior author, Gregory Storch, MD, the Ruth L. Siteman Professor of Pediatrics. "It casts a broad net and can efficiently detect viruses that are present at very low levels. We think the test will be especially useful in situations where a diagnosis remains elusive after standard testing or in situations in which the cause of a disease outbreak is unknown."
In patient samples the new test – called ViroCap – detected viruses not found by standard testing. The new test could be used to detect outbreaks of deadly viruses such as Ebola, Marburg and severe acute respiratory syndrome (SARS), as well as more mundane bugs like rotavirus and norovirus.
In evaluating the new test, researchers used biological samples of two groups of patients at St. Louis Children's Hospital. In the first sampling, standard tests found viruses in 10 of 14 patients. The new test found viruses in the four children that the other test missed, including influenza B, parechovirus, herpes virus 1 and varicella-zoster virus. In group two, eight children with unexplained fevers were tested; standard testing found 11 viruses, the new test found an additional seven, including the respiratory virus human adenovirus B type 3A.
"The test is so sensitive that it also detects variant strains of viruses that are closely related genetically," says corresponding author Todd Wylie. "Slight genetic variations among viruses often can't be distinguished by currently available tests and complicate physicians' ability to detect all variants with one test."
The researchers plan to conduct additional research to validate the accuracy of the test, so it could be several years before it is routinely available. But for now, the researchers are making the technology publicly available to scientists and clinicians worldwide.