Incidence of serum antibody titers against varicella zoster virus in Japanese patients with herpes zoster

Herpes zoster is an internal reactivation of varicella zoster virus following establishment of latent infection in the dorsal root ganglia during primary infection, which presents as chickenpox. Therefore, serologically, herpes zoster patients already have anti‐varicella zoster virus immunoglobulin G at the onset of disease. Hence, positive serum antibody does not confirm the diagnosis of herpes zoster. We retrospectively investigated the incidence of varicella zoster virus‐specific complement fixation in 865 zoster patients at initial presentation to a dermatology clinic. As a result, 66% of patients showed negative complement fixation, with patient numbers decreasing as titer increased. Paired complement fixation tests conducted within a short period showed a marked elevation in titer, and complement fixation titer gradually decreased after a year. Furthermore, incidence showed no correlation with patient age. These observations indicate that the complement fixation titer at first visit is mainly influenced by the duration from onset to presentation at clinic. Our findings indicate that a positive complement fixation result by single‐point testing confirms at least recent onset of herpes zoster, while paired tests can confirm disease when primary tests are negative.