A Comparison of Direct Immunofluorescence Method and Tzanck Test for the Diagnosis of Varicella-Zoster Virus and Herpes Simplex Virus Infections

Bahn, Jae Yong; Kwon, Sang Jin; Yu, Hee Joon; Kang, Jung Oak

Abstract

BACKGROUND: Optimal management of cutaneous varicella-zoster virus(VZV) and herpes simplex virus(HSV) infections requires rapid and accurate diagnostic method. The Tzanck test is a simple, inexpensive and rapid method, but it shows relatively low sensitivity and cannot distinguish VZV and HSV. The viral culture is the reference method, but it is time-consuming and needs cell culture facilities. Direct immunofluorescence(DIF) method has been known to be rapid and sensitive, but it has not been widely used in Korea. OBJECTIVE: We compared the usefulness of DIF method to Tzanck smear in patients with VZV and HSV infections. METHODS: Smears were collected from the base of fresh vesicular lesions, from a total of 134 patients clinically suspected of having VZV or HSV infections. The two wells of IF slide were stained with FITC-conjugated VZV-specific and HSV-specific monoclonal antibody each. Apple-green fluorescence of cytoplasm was considered positive for VZV or HSV. Glass slide smears were made for Tzanck test and stained with Wright stain. Giant cells with enlarged nucleus were considered positive. RESULTS: Among the 107 patients suspected of having VZV infection, positive rates of DIF method and Tzanck test were 91.6% and 76.6%, respectively. The positive rates of HSV in 27 patients suspected of having HSV infection, were 92.6% and 74.1%, respectively. The positive rates of DIF method were higher than that of the Tzanck test in both VZV and HSV infections. CONCLUSION: The DIF method is a more sensitive and relatively rapid method for the diagnosis of cutaneous VZV and HSV infections.