A positive PCR result in a serum test is generally considered a sign of active infection because the virus has left the cells (either because of cell death or active replication). A positive result on whole blood, however, does NOT necessarily mean an active infection because most of us have tiny amounts of latent virus circulating in the blood (10-20 copies per ml). Usually, latent virus in a healthy person can only be picked up by the more sensitive “nested” PCR on whole blood (such as the one used by Redlabs USA). Positive-nested PCR tests for HHV-6, HHV-7 and CMV (as done at Redlabs) should not be interpreted to mean that you have an active infection as many normals have low levels of DNA from these viruses in their bloodstream. Tests on whole blood (as opposed to serum/plasma) are only meaningful if they are quantitative tests that can be compared to a normal population. We hope that physicians will be able to establish a threshold for what can be considered “active” infection. See Testing page for more details.
A small percentage of the population (approximately .8% of Caucasians and .2% of Japanese) have a condition called “Chromosomally integrated HHV-6” (ciHHV-6) which means that the virus is actually integrated into your chromosomes and passed from parent to child. If you have ever had a positive PCR test, it is possible that this is due merely to your ciHHV-6 status. (See ciHHV-6 paragraph below).