The usefulness of skin test in evaluation of immunity to varicella

Kim, Ji Young; Lee, Hye Jeen; Kim, Me Jin; Kim, Young Ho; Jung, Ji A; Yang, Seung; Hwang, Il Tae; Lee, Hae Ran

Abstract

PURPOSE: The aim of this study is to assess the usefulness of skin test by an inactivated, 1/50 diluted solution of attenuated varicella vaccine in evaluating the immune status to varicella.
METHODS
Total 41 subjects (22 males, 19 females, aged 1-32 years) were enrolled from July to August, 2005. Past medical history including varicella infection, varicella vaccination were investigated through questionnaires. The skin test solution was prepared from solution of attenuated varicella vaccine(Oka strain) which was inactivated by exposure to room temperature for 10 days and diluted at 1/50 with normal saline. Skin test was done by injecting 0.1 mL of the solution intradermally into the volar surface of the right forearm and sterile normal saline was used as a control on the left forearm. Positive reaction was defined when the transverse diameter of the induration was 5 mm or more. Serum varicella zoster virus specific IgG antibody test by ELISA (enzyme-linked immunosorbent assay) was done.
RESULTS
In adults, the sensitivity of the varicella zoster virus skin test compared to ELISA was 94.7% and the positive predictive value was 100%. In children, both the positive predictive value and specificity were 100% but the sensitivity and the negative predictive value were 50% and 30.7% respectively. Children showed smaller skin test reactivity compared to adults.
CONCLUSION
The varicella zoster virus skin test using inactivated, 1/50 diluted solution of attenuated varicella vaccine was proved as one of the useful tools for evaluating the immunity and susceptibility of the varicella zoster virus.