A study published recently in the journal Science reported on an experimental blood test that needs only a small blood sample to test for past exposure to hundreds of viruses. For research purposes, where it can be helpful to know the extent of virus exposure in the population, that's a major advance over current testing, which generally checks for one virus at a time. However, this test is currently in the research stage and not available for medical use or for health practitioners to order for their patients.
In an interview with Lab Tests Online, Tomasz Kula, a graduate student at Harvard University and an author of the Science study says the test, currently called VirScan, has many important potential applications for research. The test could allow researchers to test large populations for numerous viruses, which may help provide links between viral exposures and the development of certain diseases. For example, VirScan could provide more data on the Epstein-Barr virus, which has been linked to certain cancers.
The new test works by detecting antibodies to viruses in a person's blood sample. Antibodies are produced the first time the body encounters a virus through infection or vaccination and remain in the body to generally protect against reinfection. Though the amount of some viral antibodies may wane over time if the person is not re-exposed, some persist. VirScan is a snapshot of the viral antibodies in a person's blood and may provide a good record of many of the viruses to which a person has been exposed.
In testing individuals who present with specific signs and symptoms, however, the tests probably would not be particularly useful. Knowing that a person had been exposed, at one time in their life, to a variety of different viruses would likely not help in explaining the current cause of the person's problems.
Since vaccines also cause antibody production, it would be impossible to distinguish whether antibodies to the influenza virus (or other viruses with vaccines) are due to vaccination or to past infection. Antibodies take time to develop after exposure; individuals with recently developed symptoms from a viral infection may not have antibodies at the time that they first are seen by their healthcare provider. For example, about half of persons with new hepatitis C infections do not have antibodies when they first get sick.
The study on VirScan included almost 600 people from the U.S., Thailand, South Africa and Peru who were all known to carry certain viruses, including hepatitis C and HIV. The test was over 90% accurate for those two viruses and produced very few false positives, an important factor for a medical test.
The test also detected antibodies against viruses to which study participants were not known to have been exposed. On average, the test detected antibodies to 10 different viruses in each participant. At least two people had antibodies to 84 different viruses. The most common viruses detected were cold and flu viruses and certain herpes viruses, including Epstein-Barr.
Kula says that commercialization of the test is at least several years away. Whether the test might have future applications outside of research is currently unknown. For instance, it may eventually be used to provide richer detail of what viruses are circulating in a particular community.