Role of direct immunofluorescence on Tzanck smears in pemphigus vulgaris

The Tzanck smear is a simple, sensitive, and rapid test to diagnose pemphigus vulgaris (PV), a life threatening autoimmune blistering disorder. The presence of acantholytic cells in cytology is indicative of but not specific for PV. Hence, a direct Immunofluorescence (DIF) test to demonstrate immunoglobulin deposits on the acantholytic cells would make the Tzanck test more specific, in addition to being a rapid test. Twenty untreated patients with PV confirmed histopathologically were enrolled to evaluate the efficacy of using DIF technique using IgG on Tzanck smear samples. The DIF smears were compared with DIF on skin biopsies in the same patient. This prospective pilot study approved by the institutional ethics committee was carried out in a tertiary health care hospital in a developing country. Of the 15 patients presenting within 3 mo of onset of the illness, 40% (n = 6) showed DIF positivity on Tzanck smear, when compared with 46.67% (n = 7) on skin biopsy. On the other hand, of the five patients presenting beyond 3 mo of their illness, only 20% (n = 2) showed positivity on Tzanck, when compared with all 100% (n = 5) on skin biopsy. The study, thus, suggests that DIF on skin biopsy is comparable to biopsy in diagnosing early PV. This preliminary study proposes that the use of DIF on Tzanck smear is a simple, rapid, painless, and user-friendly out-patient procedure for the diagnosis of early PV, even for relatively inaccessible lesions in the oral cavity and flexural regions. This methodology would be of great help in outlying and rural facilities lacking proper histological equipment, thus avoiding the need for a surgical or punch biopsy or heavy investment in laboratory equipment and expertise. Probable reasons for DIF negativity on Tzanck smears are also discussed.