Test: Real-Time DNA PCR on Cell-Free Sample (DNA PCR)
Due to the ubiquitous nature of human herpesviruses HHV-6, HHV-7, the use of traditional whole blood PCR methods to detect DNA in blood cells or tissue has limited value. When performed on whole blood samples, these PCR tests may detect DNA from a latent viral infection rather than an active infection associated with disease complications. In contrast, detection of high concentrations of viral DNA in cell-free samples such as plasma and cerebrospinal fluid (CSF) suggests the presence of virions or viral DNA from degenerating infected cells. Detection of herpesvirus DNA in cell-free samples is an important indicator of active tissue or central nervous system (CNS) infection.
DNA present in the cell-free sample is extracted using a commercial kit. To amplify the small amounts of relevant viral DNA present, viral “gene of interest” specific primers and probes, deoxyribonucleotides, and a thermo-stable DNA polymerase are added to the PCR reaction.