A 40 year old male repoed with recurrent episodes of oral ulcers, large areas of denuded skin and flacid vesiculo-bullous eruptions. Which is the most impoant bed-side investigation helpful in establishing the diagnosis -
D. i.e. Tzank smear
Gram staining of the blister fluid
Culture and sensitivity
Skin biopsy and immunoflurescence
Tzanck smear from the floor of bulla