Comparison of Tzanck Smear, Viral Culture, and DNA Diagnostic Methods in Detection of Herpes Simplex and Varicella-Zoster Infection

Abstract

To compare Tzanck smears, viral cultures, and DNA diagnostic methods using the polymerase chain reaction (PCR) in detection of herpes simplex virus (HSV) or varicella-zoster virus (VZV) infection in clinically suspected cases. A 12-month trial comparing PCR with viral cultures and Tzanck smears in patients with clinically suspected HSV or VZV infection. Both ambulatory and hospitalized patients were recruited from a tertiary referral center and the Miami (Fla) Veterans Affairs Medical Center. Convenience samples of patients clinically suspected to have HSV (n = 48) or VZV (n = 35). To be included in the final analysis patients needed to have a positive Tzanck smear, viral culture, or PCR result. Patients who were clinically suspected to have HSV but had VZV by viral culture or PCR were analyzed in the VZV group. Similarly, patients who were clinically suspected to have VZV, but had HSV by viral culture or PCR were analyzed in the HSV group. Seventy-seven patients were available for final analysis: HSV (n = 30), VZV (n = 32), and 15 control cases who did not have evidence of viral infection. For HSV, PCR detected HSV DNA sequences in 73% of stained smears and 83% of unstained smears. For VZV infection, VZV DNA sequences were detected in 88% of stained smears and 97% of unstained smears. Viral DNA sequences were not detected in the 15 control cases. Viral cultures were positive in 83% and 44% of HSV and VZV cases, respectively. The Tzanck smear was positive in 60% and 75% of HSV and VZV cases, respectively. PCR is a reliable method for detecting HSV and VZV DNA sequences from single stained and unstained Tzanck smears. It is clearly superior to viral culture in identifying VZV infection and is equivalent to conventional culture techniques in identifying cases of HSV.