Test Overview
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?).
How It Is Done
You will take off your clothes below the
waist. You will have a gown to drape around your waist. You will then lie on
your back on an examination table with your feet raised and supported by
stirrups. This is similar to having a pelvic examination or Pap test.
Your doctor will insert a lubricated tool called a speculum into your vagina. The speculum gently spreads apart the vaginal walls, allowing your
doctor to see the inside of the vagina and the
cervix. See a picture of the
vaginal speculum examination.
Samples of fluid inside the vagina
are then collected with a swab or wooden stick.
How It Feels
You may feel some discomfort when the
speculum is put in, especially if your vagina is irritated and tender.
Risks
There is little or no risk in having a bacterial
vaginosis test.
Results
Tests for
bacterial vaginosis take samples of fluid and cells
from the vagina to see if this vaginal infection is present.
A
high vaginal pH, clue cells, and a fishy odor usually are enough signs that
bacterial vaginosis is present.
Tests for bacterial vaginosis
| Normal |
No abnormal
vaginal discharge is present on vaginal
exam.
|
|
A wet mount does not show
large numbers of bacteria, such as Gardnerella, that
cause bacterial vaginosis.
|
|
No clue cells are
present.
|
|
No fishy odor is present when
a potassium hydroxide (KOH) solution is added to a sample of vaginal
discharge.
|
|
Vaginal
pH is in the normal range of 3.8 to 4.5.
|
| Abnormal |
A bacterial vaginosis
infection is present.
- A thin, grayish white vaginal discharge
is present on vaginal exam. The discharge often looks shiny and has small
bubbles.
- A fishy odor is made when a KOH solution is added to a
sample of vaginal discharge.
- Large numbers of the types of bacteria
that cause bacterial vaginosis (such as Gardnerella),
clue cells, or both are present on wet mount.
- Vaginal pH is greater
than 4.5.
|
What Affects the Test
Reasons you may not be able to
have the test or why the results may not be helpful include:
- If you are having your menstrual
period.
- If you use a vaginal medicine, such as a nonprescription
vaginal yeast medicine, 2 to 3 days before this test.
- Having sex or
douching 24 hours before this test.
What To Think About
- Bacterial vaginosis during pregnancy increases
a woman's risk of early (preterm) delivery. Because of this risk, it is
important to treat bacterial vaginosis during pregnancy with
antibiotics.
- Experts disagree about
calling bacterial vaginosis a
sexually transmitted infection (STI). A history of STIs
or having multiple sex partners increases the chance of developing bacterial
vaginosis. The actual number of bacterial vaginosis infections spread through
sexual contact is not fully known.
References
Other Works Consulted
- Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.
Credits
|
By
|
Healthwise Staff |
|
Primary Medical Reviewer
|
Adam Husney, MD - Family Medicine |
|
Specialist Medical Reviewer
|
Jeanne Marrazzo, MD, MPH - Infectious Disease |
|
Last Revised
|
October 22, 2012 |