Tzanck preparation is a rapid test used to help physicians diagnose infections caused by herpes viruses. This test cannot detect the virus, but can detect the characteristic changes in cells that herpes infection produces.
Herpes viruses are responsible for several superficial infections. Varicella zoster virus causes chickenpox and shingles, herpes simplex type 1 causes the common cold sore or fever blister, and herpes simplex type 2 causes the sexually transmitted disease (STD) genital herpes. All forms of herpes are associated with production of vesicles (blisters) and ulcers.
Physicians usually can diagnose herpes infections by looking at the type of vesicles and ulcers, and their distribution on the person's body. Sometimes laboratory evidence of herpes is needed to confirm the diagnosis. When a sample is available from a vesicular lesion, the Tzanck preparation can be done more rapidly and less expensively than other tests. It is important to note that herpes infection may be present in such lesions, and not produce a positive Tzanck test result. A positive finding is diagnostic of herpes infection, but is seen in only about 67% of herpes infections. Consequently, other laboratory
tests may be required to diagnose herpes infections. Some herpes infections are present in tissues that cannot be tested by a Tzanck preparation. For example, herpes can be devastating to a newborn or a person with a weakened immune system. The virus may invade the central nervous system causing meningitis. Laboratory culture, tests for herpes DNA, antigens, and antibodies may be needed for diagnosis in such circumstances.
Cell collection can be performed in minutes with only minor discomfort to the patient. Health care providers should use appropriate protective measures to avoid infection when collecting the samples.
Tzanck preparation is also called a Tzanck smear, herpes stain for inclusion bodies, or an inclusion bodies stain. The Tzanck preparation is performed by smearing cells taken from a fresh blister or ulcer onto a microscope slide. A fresh blister is opened with a scalpel or sterile needle. The physician scrapes the base of the blister with the scalpel, gathers as much cellular material as possible, and gently spreads it on a microscope slide. The cells are fixed with alcohol and stained with Giemsa stain. The cells are examined under a microscope for characteristic changes caused by herpes virus. Herpes causes formation of giant cells with multiple nuclei. The shape of each nucleus appears molded to fit together with those adjacent to it. The nuclei may also contain red inclusions characteristic of herpes infection.
There is no special preparation required before this procedure.
There are no special aftercare requirements associated with this procedure.
There are no complications associated with this procedure. However, health care professionals should be careful not to expose themselves to the potentially infectious material during specimen collection.
A normal smear shows no evidence of a herpes infection. However, this test may also produce false negatives. Studies have shown that the Tzanck preparation shows signs of infection in only 50–79% of people with a herpes infection. A negative Tzanck preparation may have to be confirmed by a herpes culture or other laboratory test. A smear that shows evidence of herpes infection does not distinguish between the various infections caused by herpes virus. The physician uses the person's symptoms and other clinical findings to distinguish between these infections and will often order a culture for confirmation. Newer antigen detection tests and serologic tests are available to assist in diagnosing herpes viruses, but viral cultures are still considered the best and most cost efficient diagnostic tool available.
Health care team roles
A physician, nurse, or physician assistant collects the cell samples from the patient. The Tzanck preparation and microscopic examination may be performed by the physician, by a clinical laboratory scientist/medical technologist, or laboratory specialist with specific training in clinical diagnostic virology.
The health care provider can be an important resource for patients with herpes infection, especially those with genital herpes. Patients with genital herpes may be embarrassed about their condition or hesitant to seek medical attention. Health care providers counsel patients, and explain prevention and treatment of sexually transmitted diseases.
Herpes—A family of viruses including herpes simplex types 1 and 2, and herpes zoster (also called varicella zoster). Herpes viruses cause several infections, all characterized by blisters and ulcers, including chickenpox, shingles, genital herpes, and cold sores or fever blisters.
Costello, Michael, and Margaret Yungbluth. "Viral Infections." In Clinical Diagnosis and Management by Laboratory Methods. 20th ed., edited by John Bernard
Parker, Frank. "Diagnostic Tests and Aids in Examination of the Skin." In Cecil Textbook of Medicine. 21st ed., edited by Lee Goldman and J. Claude Bennett. Philadelphia: W.B. Saunders Company, 2000, p. 2271.
Emmert, David H. "Treatment of Common Cutaneous Herpes Simplex Virus Infections." American Family Physician 61 (March 15, 2000): pp.1697-1708.
American Social Health Association. PO Box 13827, Research Triangle Park, NC 27709. (919) 361-8400. <http://www.ashastd.org>.
Division of Sexually Transmitted Diseases, National Center for HIV, STD and TB Prevention, Centers for Disease Control and Prevention. 1600 Clifton Road NE, Atlanta, GA 30333. (800) 311-3435. <http:/www.cdc.gov>.
Linda D. Jones, B.A., PBT (ASCP)