Comparison of Tzanck Test and Polymerase Chain Reaction in the Diagnosis of Herpes Simplex Virus and Varicella Zoster Virus infections

Kim, Jin Ki; Lee, Hee Jung; Kim, Dong Hyun; Yoon, Moon Soo

Abstract

BACKGROUND
Herpes simplex virus (HSV) and varicella zoster virus (VZV) are two of the most common causes of mucocutaneous vesicular eruptions. Their diagnoses are usually made clinically, but the clinical distinction between HSV and VZV is sometimes difficult.
OBJECTIVE
We investigated the usefulness of polymerase chain reaction (PCR) and Tzanck test in patients with HSV and VZV infections.
METHODS
From June 2008 through June 2010, a total of 396 patients (53 patients with HSV and 343 patients with VZV) were included in this study. Wright-stained smears of scrapings from the base of skin lesions and viral DNA amplification by PCR were examined in all patients. We compared the positivity rates of Tzanck test and PCR according to virus type and duration of skin lesions.
RESULTS
The overall positivity rates of Tzanck test and PCR were 56.6% and 86.9%, respectively, and the difference between the positivity rates of the two tests was statistically significant (p<0.0001). The Tzanck test was positive in 41.5% and 58.9% of the HSV and VZV cases, respectively, and the difference was statistically significant (p=0.0259). For PCR, there were no significant differences between the HSV and VZV cases. The positivity rate of the Tzanck test decreased in the old skin lesions over 7 days; however, PCR method showed no significant differences in positivity rates according to duration of the skin lesions.
CONCLUSION
PCR is a more sensitive method for the diagnoses of HSV and VZV infections, and it can be utilized for diagnosis even of old skin lesions.