Two types of herpes simplex virus (HSV) are responsible for common, often oral (mostly HSV-1, rarely HSV-2) and genital (mostly HSV-2, but also HSV-1) infections. HSV infections are permanent and the virus can reactivate multiple times. Detecting the virus in a lesion is the best way to diagnose an acute HSV infection. The PCR herpes test (polymerase chain reaction), also known as the nucleic acid amplification technique (NAAT), involves multiplying the number of copies of the virus’s nucleic acid to better detect its presence. This approach is the most sensitive for detecting types 1 and 2 of the virus. Results also include testing for the herpes subtype responsible for chicken pox and shingles (herpes zoster or varicella zoster). The technique is highly sensitive and produces positive results in more than 95% of lesions where HSV-1 or 2 are present.
A positive result confirms an acute HSV-1 and/or HSV-2 infection in the sampled lesion. Although false negative results are very rare, they can occur when the number of copies of the virus is very low in the sample or it does not actively multiply. False positive results are also very rare.