What is a Wet Mount or Vaginal Smear?

Clue cells are vaginal epithelial cells that are covered in bacteria. They are one way of diagnosing bacterial vaginosis. Photo Courtesy of the Public Health Image Library; CDC/M. Rein

Definition: In the context of women's health, a wet mount is a slide made from a vaginal swab. It is also known as a vaginal smear.

To prepare a wet mount, your doctor will swab your vagina -- usually during a pelvic exam -- and roll the swab onto a slide. Then she can look at the wet mount under her office microscope to diagnose visible conditions such as bacterial vaginosis and trichomoniasis.

Wet mounts are not used to diagnose most common STDs such as chlamydia and gonorrhea.

However, these vaginal smears can give your doctor important insights about your reproductive health.

Examples: Back when I was in graduate school, I had to read wet mounts from hundreds of women as part of my thesis research on vaginal flora. I looked at vaginal smear after vaginal smear and one day was stunned to find a sperm on a wet mount. I stared at it in confusion for 5 minutes, unable to figure out what it was doing there. I had completely forgotten that some people actually have sex without using a condom.

Clarifying The Difference Between Wet Mounts and Pap Smears

Wet mounts and Pap smears may both start with a swab, but they're very different types of tests. Wet mounts are read in the office setting by the physician, and they are used to detect 3-4 specific types of infections including yeast infections, BV, and trichomoniasis. They require training, but are relatively easy to perform.

Pap smears, on the other hand, aren't used to detect STDs. Instead, they're used to detect pre-cancerous cervical changes that are associated with HPV. They are a test for cancer, and pre-cancer, and although the cervical swabs are taken in the doctor's office, they are read by specially trained pathologists (or computers.) The differences are much more subtle than the changes doctors are looking for on a wet mount.

The other important difference between Pap smears and wet mounts is that Pap smears are swabs of the cervix, while wet mounts are swabs of the vagina. They're not only looking for different types of conditions, they're looking in different places.

On the other hand, one thing that both wet mounts and Pap smears have in common is that they're done alongside other STD tests. Neither test stands on its own for managing a woman's sexual health.

Sources:

Mylonas I, Bergauer F. Diagnosis of vaginal discharge by wet mount microscopy: a simple and underrated method. Obstet Gynecol Surv. 2011 Jun;66(6):359-68. doi:10.1097/OGX.0b013e31822bdf31.

Smith RA, Manassaram-Baptiste D, Brooks D, Doroshenk M, Fedewa S, Saslow D, Brawley OW, Wender R. Cancer screening in the United States, 2015: a review of current American cancer society guidelines and current issues in cancer screening. CA Cancer J Clin. 2015 Jan-Feb;65(1):30-54. doi: 10.3322/caac.21261.

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