Cytology is a rapid method of evaluation that can be used in cases in which the diagnosis is uncertain. Fluorescent-antibody stained smears using fluorescein conjugated monoclonal antibodies is more reliable than is routine cytology and is positive in
over 80% of cases. The most accurate method of diagnosis is viral isolation in tissue culture, but this test is more expensive and the results take days rather than hours. Demonstration of a rising antibody titer is rarely necessary for diagnosis except in cases of zoster sine eruptione, when it is the only means of confirming suspected cases.