Bacterial Vaginosis Test

What is a bacterial vaginosis (BV) test?

A bacterial vaginosis (BV) test checks for a bacterial infection in the vagina. A healthy vagina contains more healthy (“good”) bacteria than unhealthy (“harmful”) bacteria. But if you have bacterial vaginosis, the harmful bacteria grow more than the good bacteria. This upsets the healthy balance and can cause an infection.

A BV test checks for bacterial vaginosis by measuring the amount of harmful bacteria in a sample of vaginal discharge (fluid that comes out of the vagina). There are different ways to check a sample for signs of BV. These include:

• Vaginal smear (also called wet mount). In this test, the sample is prepared on a glass slide and checked under a microscope for bacteria, white blood cells, and other cells that are signs of infection.
• Whiff test. In this test, the sample is mixed with a chemical to see if it makes a strong, fishy odor, which is a sign of BV.
• Vaginal pH test. This test checks the acidity of the sample. High acidity is a sign of BV. But a pH test alone can't diagnose BV, so it's used with other tests.
• PCR test. This test checks your sample for genetic material from harmful bacteria. It's used less often than the other three tests because it costs more and takes longer to get results.

Other names: vaginal pH test, KOH test, wet mount test

What is it used for?

A BV test is used to find out if bacterial vaginosis is the cause of symptoms that appear to be from a vaginal infection.

Any woman can get BV, even women who have never had sex. However, it's most common in women who are sexually active, especially in those who:

• Have new or multiple sex partners
• Use douches (rinsing the vagina with water or other fluid)
• Don't use condoms
• Have an intrauterine device (IUD)

Each of these risk factors can upset the normal balance of bacteria in the vagina and lead to BV. If you are sexually active, you can reduce your risk by limiting your number of sex partners, not using douches, and using condoms every time you have sex.

Why do I need a BV test?

You may need testing if you have symptoms of BV. These include:

• An unusual vaginal discharge that can be gray, white, foamy, or watery
• A strong, fish-like odor, especially after sex
• Pain and/or itching in the vagina
• Itching around the outside of the vagina
• Burning feeling when urinating (peeing)

Sometimes a BV infection doesn't cause symptoms, and it can go away on its own. But serious health problems are linked to untreated BV. If you have symptoms, testing and treatment can help avoid the increased risk of:

• Getting a sexually transmitted infection (STI). BV makes your vagina more acidic than normal, which increases your chance of getting STIs, such as chlamydia, genital herpes, gonorrhea, or HIV. And if you have HIV and BV, you're more likely to pass HIV to your sex partner.
• Preterm birth. If you have a BV infection during pregnancy, it can increase the chance that your baby will be born too early (premature) or have a low birth weight. Low birth weight can cause serious health problems for your baby, including difficulty breathing, gaining weight, and fighting infections.

You may also need a test if:

• You have a female sex partner who has BV or symptoms that could be BV
• You've given birth to a preterm baby before and are pregnant again (even if you don't have symptoms of BV)

What happens during a BV test?

A BV test is done much like a pelvic exam:

• You'll take off your clothes below your waist and wear a gown or use a sheet as a cover.
• You'll lie on an exam table with your feet in stirrups.
• Your health care provider will use a plastic or metal instrument called a speculum to gently widen your vagina so the cervix can be seen.
• Your provider will use a cotton swab or wooden stick to collect a sample of your vaginal discharge.
• Your provider may examine the sample or send it to a lab for testing.

At-home test kits are available to test for the bacteria that cause BV. The kits include everything you need to collect a sample of vaginal fluid and send it to a lab for testing. To get proper care, share your results with your provider.

There are also at-home vaginal pH test kits. These kits use a swab or paper strip that changes color after you moisten it with vaginal fluid. A chart shows you what pH level each color means. Higher pH levels are less acidic, meaning bacteria can more easily grow. So, if you do have a high pH, it may mean you have BV. However, a pH test kit alone can't diagnose BV. To be sure about your results, discuss them with your provider.

Will I need to do anything to prepare for the test?

Follow the instructions your provider gives you to prepare for this test. For 24 hours before your test, you'll usually need to avoid:

• Using tampons
• Douching
• Using creams or medicines in the vagina
• Having vaginal sex

Are there any risks to the test?

You may feel mild discomfort when the speculum is put in your vagina.

What do the results mean?

The results from a BV test may be reported in different ways depending on the type of test you received. The results of a:

• Vaginal smear or a whiff test will be reported as either “normal” or “abnormal.” If the results are abnormal, that means that you have a bacterial infection.
• Vaginal pH test will be a number that shows how acidic your vagina is. A healthy vagina has a pH range between 3.8 and 4.5. A pH over 4.5, may mean you have BV. However, a pH test can't diagnose BV on its own.

If your results show you have a BV infection, your provider will probably prescribe antibiotic pills and/or antibiotic creams or gels that you put in your vagina. Medicines that treat BV are safe to use during pregnancy.

Sometimes a BV infection will come back after successful treatment. If this happens, your provider may prescribe different medicine or a different dose of the medicine you took before. If you're diagnosed with BV and have a male sex partner, he may also need to be treated with antibiotic pills or creams/gels. This is because treating a male sex partner can lower your chance of getting BV again.

There are no over-the-counter treatments for BV. Treatments for vaginal yeast infections will not help BV and could make your symptoms worse. So, don't try to treat an infection yourself.

If your results show you don't have BV, your provider may do more tests to find the cause of your symptoms.

If you have questions about your results, talk with your provider.

Learn more about laboratory tests, reference ranges, and understanding results.