Sexual Conditions Health Center

Tests for bacterial vaginosis take samples of fluid and cells from the vagina to see if this vaginal infection is present. Bacterial vaginosis has also been called nonspecific vaginitis, Haemophilus vaginitis, or Gardnerella vaginitis.

Bacterial vaginosis is caused by a change in the balance of microorganisms found in a healthy vagina. A healthy vagina normally has many microorganisms in it. The microorganisms involved in bacterial vaginosis include Gardnerella, Mobiluncus, Bacteroides, and Mycoplasma. When bacterial vaginosis is present, these microorganisms increase in number while the number of healthy microorganisms decrease.

Many women with bacterial vaginosis do not have symptoms. The most common symptom of bacterial vaginosis is an increase in a grayish white vaginal discharge, unlike normal vaginal discharge. The discharge often has a fishy smell.

Women who have bacterial vaginosis during pregnancy have a higher chance of miscarriage, early (preterm) delivery, and an infection after delivery, so it is important for pregnant women who have symptoms to be tested for bacterial vaginosis.

Several tests can be used to find bacterial vaginosis:

• Wet mount. A sample of vaginal discharge is mixed with a salt solution on a microscope slide. The slide is checked for bacteria, white blood cells, and unusual cells called clue cells. If clue cells are present, it means bacterial vaginosis is present.
• Whiff test. Several drops of a potassium hydroxide (KOH) solution are added to a sample of vaginal discharge to see whether a strong fishy odor is produced. A fishy odor on the whiff test usually means bacterial vaginosis is present.
• Vaginal pH. The normal vaginal pH is 3.8 to 4.5. Bacterial vaginosis often causes the vaginal pH to be greater than 4.5.
• Oligonucleotide probes. This test finds the genetic material (DNA) of this bacteria. An oligonucleotide probe test is very accurate but is not available in all labs.

Bacterial vaginosis may be found during a Pap test. But a Pap test is not recommended as a test to find bacterial vaginosis.

Why It Is Done

Tests for bacterial vaginosis are done to help find the cause of an abnormal vaginal discharge or other symptoms of a vaginal infection, such as vaginal irritation or pain.

How To Prepare

Do not douche, have sex, or use vaginal medicines for 24 hours before having a bacterial vaginosis test.

These tests are not usually done during your menstrual period.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).