Tests for Bacterial Vaginosis
Tests for bacterial vaginosis take samples of fluid and cells from the vagina to see if signs of infection are present.
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 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 may be 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 routinely used to diagnose bacterial vaginosis.
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.