The diagnostic process begins with a physical exam, including a pelvic exam, and a medical history. The doctor will want to know about a woman's symptoms, symptom duration and frequency, prescribed medications (such as antibiotics or oral contraceptives), and any over-the-counter treatments the woman may have tried. The doctor may ask the woman about personal habits (douching, use of feminine products or scented soaps, tight clothing, etc.) and about sexual practices. From this information, a decision may be made about what type of testing should be performed.
The goals with testing are to diagnose vaginitis/vaginosis and to determine the underlying cause in order to help guide treatment. Testing is also used to evaluate the best treatment options in those who do not respond to initial therapy and/or who have recurrent episodes.
Clinical diagnosis of bacterial vaginosis is based on the Amsel criteria, where three of the four following symptoms are present:
- Grayish-white vaginal discharge
- Vaginal pH greater than 4.5
- Presence of "clue" cells as determined by a wet prep (see below)
- Fishy odor present with the addition of 10% potassium hydroxide (whiff test below)
A few testing methods may be performed in a doctor's office or medical clinic by the health care practitioner, or a sample may be collected and sent to a laboratory.
The "gold standard" for the diagnosis of bacterial vaginosis is the direct examination of the vaginal secretions, which can be viewed microscopically as an unstained wet mount or as a Gram stained slide.
Wet Prep (Wet Mount/Smear)
A drop of vaginal discharge is placed on a glass slide and then examined under the microscope. Examples of typical findings include:
- Bacterial vaginosis—the presence of "clue cells," which are vaginal epithelial cells with most of the surface covered by bacteria, and the presence of few to no white blood cells (WBCs) are characteristic.
- Candidiasis—yeast may be seen as budding yeast and/or tube or branch-like structures (pseudohyphae).
- Trichomoniasis—these are parasites that can be seen as oval bodies with hair-like structures (flagella) that move. An increased number of WBCs may also be seen.
Vaginal fluid is placed on a glass slide and specially stained (Gram stain). The specimen is observed under a microscope for certain bacterial cell types (morphotypes) and the evaluation is based on the abundance of each type of bacteria. If 20% or more of the epithelial cells are covered by bacteria ("clue cells"), this is diagnostic for bacterial vaginitis. A decrease in the number of normal bacterial cells such as Lactobacillus species is associated with bacterial vaginosis. The presence of yeast cells can also be detected with a Gram stain, while the parasite Trichomonas is not detected by this method.
Other critical tests on the sample include the following:
Vaginal discharge is checked for pH.
- A pH of less than 4.5 is normal but can also be seen with a yeast infection (candidiasis).
- An increased pH (such as greater than 5.0) may be seen with bacterial vaginosis and with trichomoniasis.
Whiff (or Sniff) Test and KOH Prep
A sample of the vaginal discharge is placed on a glass slide with a drop of 10% potassium hydroxide (KOH).
- Bacterial vaginosis: chemical compounds called amines will be released, causing a fishy odor.
- Candidiasis: budding yeast and pseudohyphae can often be seen more easily.
- Trichomoniasis: can also release an unpleasant odor.
- Bacterial vaginal cultures should be discouraged for the diagnosis of bacterial vaginitis. Gardnerella vaginalis can be cultured from 50-60% of healthy, asymptomatic women and therefore the growth of these bacteria in culture is difficult to interpret.
- Candidiasis: a fungal culture may be ordered to help guide treatment with persistent or recurrent infections and can be used to identify which yeast is present.
- Trichomoniasis: a special trichomonas culture may be performed to detect trichomonads when microscopic exam is not sufficient.
Additional test methods are available for identifying the causes of vaginitis/vaginosis, such as:
- Molecular methods (e.g., nucleic acid amplification, NAAT) for identifying trichomonas, yeast or bacterial vaginosis.
- Rapid point-of-care tests for detecting trichomonas or bacterial vaginosis
If someone has trichomoniasis and/or STDs are suspected, additional testing may be performed, including use of highly specific polymerase chain reaction (PCR) testing to check for other STDs, such as:
If a person has recurrent yeast infections, follow-up testing may be performed to look for underlying conditions that may be contributing to the vaginitis/vaginosis, such as diabetes.
Other than a physical examination, other non-laboratory tests, such as imaging, are usually not required for diagnosing vaginitis/vaginosis. However, if a serious complication such as pelvic inflammatory disease (PID) is suspected, then a pelvic or transvaginal ultrasound may be performed. This test may reveal the presence of enlarged fallopian tubes or an abscess.