Is a low vaginal swab or high vaginal swab preferred for diagnosing Bacterial Vaginosis (BV)?

From the Guidelines

For diagnosing bacterial vaginosis (BV), a low vaginal swab is generally preferred over a high vaginal swab. The low vaginal swab, taken from the lower third of the vagina, is sufficient because BV affects the vaginal ecosystem broadly rather than being localized to the upper vagina 1. When collecting a sample, a clinician should use a cotton or dacron swab to sample the lower vaginal walls, avoiding lubricants that might interfere with testing. The swab should be placed in appropriate transport medium if not tested immediately. BV diagnosis typically involves microscopic examination for clue cells, pH testing (BV typically shows pH >4.5), whiff test with potassium hydroxide, and assessment of vaginal discharge characteristics. The Amsel criteria or Nugent scoring system can then be applied to these findings. Low vaginal swabs are also more convenient, less invasive, and can be self-collected by patients in some cases. The rationale for using low vaginal swabs is that BV represents an imbalance of the normal vaginal flora with overgrowth of anaerobic bacteria and reduction in lactobacilli, which affects the entire vaginal canal rather than just the upper portion.

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) 1
• The use of a DNA probe based test for high concentrations of G. vaginalis may have clinical utility 1

It's also important to note that treatment of the male sex partner has not been beneficial in preventing the recurrence of BV 1. Additionally, women who have never been sexually active are rarely affected by BV 1.

In terms of diagnostic methods, the Amsel criteria or Nugent scoring system can be used to diagnose BV 1. The Amsel criteria require three of the following symptoms or signs: 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. The Nugent scoring system is based on the microscopic examination of a Gram-stained vaginal smear.

Overall, the use of a low vaginal swab is a convenient and effective method for diagnosing BV, and can be used in conjunction with other diagnostic methods to confirm the diagnosis.

From the Research

Bacterial Vaginosis Diagnosis

• The diagnosis of bacterial vaginosis (BV) can be made using various methods, 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 2.
• The Amsel criteria are commonly used for the diagnosis of BV, but other methods such as Gram stain analysis and molecular diagnostics are also available 3, 4.
• Point-of-care tests, such as the BVBlue test, have been evaluated for the diagnosis of BV and have shown good sensitivity and specificity compared to conventional diagnostic methods 5.

Vaginal Swab Collection

• The collection of vaginal swabs is an important step in the diagnosis of BV, but the optimal method for collecting these swabs is not specified in the available evidence.
• Vaginal swabs can be collected for quantitative vaginal culture, as well as for Gram stain analysis and molecular diagnostics 3, 4, 6.
• The evidence does not provide a clear recommendation for the use of low vaginal swabs or high vaginal swabs for the diagnosis of BV.

Treatment of Bacterial Vaginosis

• The treatment of BV typically involves the use of topical or oral antibiotics, such as clindamycin or metronidazole 2, 6.
• The choice of treatment may depend on various factors, including the severity of symptoms, the presence of other infections, and the patient's medical history.
• The evidence suggests that both clindamycin and metronidazole are effective treatments for BV, but they may have differing effects on the vaginal microflora 6.