From the Guidelines
Bacterial vaginosis (BV) should be diagnosed by meeting at least three of the four clinical criteria: a homogeneous, white, noninflammatory discharge that smoothly coats the vaginal walls; the presence of clue cells on microscopic examination; a pH of vaginal fluid >4.5; and a fishy odor of vaginal discharge before or after addition of 10% KOH (i.e., the whiff test) 1. To diagnose BV, a healthcare provider will typically perform a pelvic examination and collect a vaginal discharge sample for evaluation. The diagnosis can also be made using a Gram stain of vaginal discharge, which determines the relative concentration of the bacterial morphotypes characteristic of the altered flora of BV 1. Some key points to consider when diagnosing BV include:
- The presence of a homogeneous, white, noninflammatory discharge that smoothly coats the vaginal walls
- The presence of clue cells on microscopic examination
- A pH of vaginal fluid >4.5
- A fishy odor of vaginal discharge before or after addition of 10% KOH (i.e., the whiff test)
- The use of a Gram stain to determine the relative concentration of the bacterial morphotypes characteristic of the altered flora of BV It's also important to note that culture of G. vaginalis is not recommended as a diagnostic tool because it is not specific, but a DNA probe based test for high concentrations of G. vaginalis may have clinical utility 1. Common symptoms that might prompt testing include abnormal vaginal discharge with a fishy odor, particularly after intercourse, vaginal itching, and burning during urination, though some women remain asymptomatic 1. It's essential to seek proper diagnosis rather than self-treating, as symptoms can mimic other vaginal infections like yeast infections or sexually transmitted infections, which require different treatments.
From the FDA Drug Label
For purposes of this indication, a clinical diagnosis of bacterial vaginosis is usually defined by the presence of a homogeneous vaginal discharge that (a) has a pH of greater than 4.5, (b) emits a “fishy” amine odor when mixed with a 10% KOH solution, and (c) contains clue cells on microscopic examination. A clinical diagnosis of bacterial vaginosis was based on Amsel's criteria and defined by the presence of an abnormal homogeneous vaginal discharge that (a) has a pH of greater than 4.5, (b) emits a "fishy" amine odor when mixed with a 10% KOH solution, and (c) contains ≥20% clue cells on microscopic examination.
To diagnose bacterial vaginosis, the following criteria should be met:
- The presence of a homogeneous vaginal discharge
- A pH of greater than 4.5
- A "fishy" amine odor when mixed with a 10% KOH solution
- The presence of clue cells on microscopic examination, with ≥20% clue cells for a diagnosis based on Amsel's criteria 2 3. Gram stain results consistent with a diagnosis of bacterial vaginosis include:
- Markedly reduced or absent Lactobacillus morphology
- Predominance of Gardnerella morphotype
- Absent or few white blood cells. Other pathogens commonly associated with vulvovaginitis should be ruled out.
From the Research
Diagnosis of Bacterial Vaginosis
To diagnose bacterial vaginosis, several methods can be used, including:
- The Amsel criteria, which include vaginal pH greater than 4.5, positive whiff test, milky discharge, and the presence of clue cells on microscopic examination of vaginal fluid 4, 5, 6, 7
- The Nugent scoring system, which is considered the gold standard for diagnosing bacterial vaginosis, but is time consuming and costly 6
- Microscopic examination of vaginal fluid, which can help identify clue cells and other characteristics of bacterial vaginosis 4, 5
Amsel Criteria
The Amsel criteria are a set of clinical criteria used to diagnose bacterial vaginosis, and include:
- Vaginal pH greater than 4.5
- Positive whiff test
- Milky discharge
- Presence of clue cells on microscopic examination of vaginal fluid These criteria can be used individually or in combination to diagnose bacterial vaginosis, and have been shown to be accurate and reliable 6, 7
Comparison of Diagnostic Methods
Studies have compared the accuracy of different diagnostic methods for bacterial vaginosis, including the Amsel criteria and the Nugent scoring system 6, 7
- The Amsel criteria have been shown to have a sensitivity of 0.91, specificity of 0.91, positive predictive value of 0.86, and negative predictive value of 0.94, compared to the Nugent scoring system 6
- The combination of two Amsel criteria has been shown to have a sensitivity of 83% to 93%, and specificity of 82% to 94% 7
Treatment and Diagnosis
Diagnosis of bacterial vaginosis is important for guiding treatment, which typically involves oral or topical antibiotics such as metronidazole or clindamycin 4, 5, 8
- Treatment options for bacterial vaginosis have been shown to be effective in eradicating the infection, but may have varying rates of cure and side effects 8