[Virologic diagnosis of herpes zoster]

Diagnosis of herpes zoster needs to be rapid when effective antiviral chemotherapy is being considered. Patients with atypical clinical features can often only be diagnosed by virological methods. In the present study, vesicle specimens of 100 patients with zoster were analysed by detecting viral DNA using polymerase chain reaction (PCR). The findings were compared with those obtained by traditional virological and serological methods. PCR results confirmed the clinical diagnosis of zoster in 95%. Primers selected from varicella-zoster virus (VZV) gene 28 proved to be most sensitive. The sensitivity of virus culture was 20% (specificity 100%) and of direct immunofluorescent VZV-specific antigen staining in vesicle samples 82% (specificity 76%). There was a serological response to specific IgM and IgA antibodies in 48% within four days after the onset of rash. These findings suggest that PCR is the method of choice for rapid laboratory diagnosis of zoster.