From the Research
The false positive rate for Varicella Zoster Virus (VZV) PCR testing is extremely low, typically less than 1%. PCR testing for VZV is highly specific, with specificity rates often exceeding 99% 1. This means that when a positive result is obtained, it is very likely to be a true positive indicating the presence of VZV. The high reliability of VZV PCR testing is why it has become the gold standard for diagnosing VZV infections, replacing older methods like viral culture.
The test works by detecting viral DNA in clinical specimens such as vesicular fluid, skin lesions, cerebrospinal fluid, or blood. False positives can occasionally occur due to laboratory contamination, sample mix-ups, or technical errors during processing. When interpreting VZV PCR results, clinicians should always correlate the laboratory findings with clinical presentation. If there is a discrepancy between a positive PCR result and clinical features not typical of VZV infection, repeat testing may be warranted.
Some key points to consider when evaluating VZV PCR results include:
- The high specificity of VZV PCR testing provides confidence in positive results and helps guide appropriate antiviral therapy with medications like acyclovir, valacyclovir, or famciclovir 2, 3, 4.
- PCR testing of skin lesion specimens remains convenient and accurate for diagnosing varicella disease in vaccinated and unvaccinated persons 1.
- The emergence of VZV resistance to acyclovir can be managed with alternative antiviral agents like famciclovir 4 or new molecules such as amenamevir 3.
Overall, VZV PCR testing is a highly reliable and specific diagnostic tool, and its results should be interpreted in the context of clinical presentation and medical history.