Cytodiagnostic smear.

To diagnose infections caused by several types of herpesviruses, particularly shingles, chicken pox, and herpes simplex.

The herpesvirus can cause certain skin cells to become abnormally large or develop other abnormalities. These cells, taken from a blister caused by the virus, can be seen under a microscope.

None.

A blister that is typical of the infection is burst, and its bottom and top are scraped and smeared onto a microscope slide.

You are free to resume normal activities. The slide is stained with dyes and examined under a microscope, either in the doctor's office or in a hospital or commercial laboratory.

The stage of the blister. If the sample is taken when the blister is healing, the likelihood of detecting the virus decreases.

Although the virus itself is not detected with this test, the presence of certain abnormally large cells can confirm the diagnosis. When results are negative, however, herpes cannot be ruled out.

Results are received faster than with the culture test.

False-negative results occur in about one-third of cases.

The presence of certain cells definitively diagnoses herpes, which can then be treated. If the results are negative, a culture may be done, or the doctor may use that information to support a conclusion that a herpesvirus infection is not present.