Nested multiplex polymerase chain reaction for the diagnosis of cutaneous herpes simplex and herpes zoster infections and a comparison with electronmicroscopy.

Herpes simplex virus (HSV) and varicella zoster virus (VZV) are common causes of cutaneous and mucocutaneous vesicular eruptions. Laboratory diagnostic techniques include Tzanck smears, electronmicroscopy, antigen detection and viral culture. This paper describes a nested multiplex polymerase chain reaction with respective sensitivities of 0.0001, 0.01 and 0.1 TCID50 for VZV, HSV-1 and HSV-2. The assay was used in (a) a salvage capacity for slides already processed for electronmicroscopy, and (b) as a front-line assay for prospectively processed specimens. Sixty-two glass slides with vesicle lymph/scrapings from 58 patients with suspected cutaneous herpetic lesions were examined. The clinical presentations were described as atypical/not specified (24), VZV (20) or HSV (18), and involved eruptions from diverse anatomical sites, including the genitalia. Of the 62 specimens, 6 and 38 were positive by electronmicroscopy and multiplex PCR respectively, giving a comparative sensitivity of 16% for electronmicroscopy. Nested multiplex PCR identified 15 VZV and 20 HSV-1 infections. Where the clinical details indicated either HSV or VZV (38/62), nested multiplex PCR was statistically likely to be reactive (26/38 vs. 9/24) (chi2 P = 0.000004) whereas electronmicroscopy was not (4/38 vs. 2/24) (chi2 P= 0.77). Where the clinical details indicated VZV (20/62) or HSV (18/62), nested multiplex PCR was statistically more likely to confirm VZV (10/20 vs. 5/42) (chi2 P= 0.001) or HSV (9/18 vs. 11/44) (chi2 P = 0.05) respectively. Two suspected HSV and 6 suspected VZV infections were shown to be VZV and HSV respectively by nested multiplex PCR.