Which Lab Test Can Detect Bacterial Vaginosis?

An easy way to tell if someone has bacterial vaginosis is to do a whiff or amine test. When vaginal fluid is mixed with potassium hydroxide, it gives off a fishy smell, which is how the term “Whiff test” came about.

• Sample Collection: A healthcare worker uses a swab to get a small amount of vaginal waste, usually from the back of the vagina.
• Preparation: A drop of a 10% potassium hydroxide (KOH) solution is added to the sample after the swab is placed on a glass slide. Because KOH is alkaline, it helps get rid of the amines, which are chemical substances that bacteria make and are linked to bacterial vaginosis.
• Observation: The medical expert continues to sniff the mixture. Someone will smell something strong and fishy right after the KOH is added if a good result is found. When bacteria that cause bacterial vaginosis break down, they create volatile amines like putrescine and cadaverine, which give the urine its smell.

The pH test checks how acidic or basic the vaginal discharge is, which is very important for vaginal health.¹ The pH test finds bacterial vaginosis by showing that the vaginal environment is more alkaline.

This is how the pH test generally works:

• Sample Collection: Vaginal discharge is collected by a clinician during sample collection. A gently sterile swab inserted and removed from the vagina is common.
• pH Measurement: Sample pH is tested with a strip or paper. The pH-sensitive dye in these strips changes color with sample acidity or alkalinity. Color charts indicate pH and color variations.
• Interpretation: Vaginal discharge is normally 3.8–5 acidic.² Vaginal infections like bacterial vaginosis may occur at pH exceeding 5. In bacterial vaginosis, bacteria overgrow, diminishing vaginal acidity-keeping lactobacilli. Alkaline pH.

Samples need to be looked at under a microscope to confirm bacterial vaginosis. A sample of vaginal fluid is looked at under a microscope to find germs and changes in cells that are linked to BV. Full breakdown of the process:

• Sample Collection: The doctor takes a clean swab of the discharge from the uterus. Since most of the discharge is focusing on the vaginal walls, a sample is taken.
• Slide Preparation: The object is put on a glass slide in a flat pattern and told to dry naturally. A saline solution could be added to the sample to help the lens see the details of the cells better.
• Staining: To color dried samples, you use Gram stain. This method helps figure out what germs and cells are in a sample. Gram stain testing helps find clue cells that show that a woman has bacterial vaginosis.
• Microscopic Examination: The dyed slide is looked at in the sun by a doctor or lab tech. The following traits will be looked for:
  • Clue Cells: These vaginal epithelial cells are cloudy or grainy because bacteria cover them. Clue cells are very important for diagnosing bacterial vaginosis.³
  • Lactobacilli: Lactobacilli that are long and rod-shaped are what make up a healthy vaginal environment.⁴ Less lactobacilli may be a sign of an imbalance in the vaginal flora, which is common in BV.
  • Other Bacteria: Gardnerella vaginalis, a rod-shaped bacteria, can also be a sign of BV.
• Interpretation: The results of the microscopic test are judged by looking at the patient’s symptoms and other medical factors. A positive Whiff test, clue cells, and an increase in vaginal pH can all show that you have bacterial vaginosis.

These molecular diagnostic tests find DNA or RNA from bacteria and viruses. By recognizing their DNA or RNA, NAATs can find bacterial vaginosis bugs.

An in-depth look at NAATs for bacterial vaginosis:⁵

• Sample Collection: A doctor swabs fluid from the uterus. Put the sample in a shipping medium to keep the genetic material safe until it can be tested.
• Extraction: To get the bacteria’s genetic material out of the sample, a chemical method is used. This method separates the genetic material from the sample, which makes it easier to find.
• Amplification: NAATs need to take genetic material out and make it bigger. A piece of bacterial DNA or RNA is copied with enzymes. A popular way to increase the amount of NAAT is to use polymerase chain reaction.
• Identification: To find increased genetic material, different types of NAAT use different methods. This could be done with probes that show when they link to certain genetic material or visible dyes that stick to DNA or RNA.
• Interpretation: Bacteria that cause bacterial vaginosis are shown by positive test results. If the readings are not positive, it means that these germs are not present.

The Amsel Diagnostic Criteria tells doctors how to tell if someone has bacterial vaginosis. It was made by the team led by Dr. Robert P. Amsel in the 1980s. If you meet three of these four conditions, you may have bacterial vaginosis:

• Homogeneous Vaginal Discharge: Vaginal discharge that is homogeneous is thin and white, and it covers the walls evenly. The vaginal discharge that changes with each period is different from the “milky” or “creamy” discharge.
• Vaginal pH Greater than 5: Most of the time, vaginal pH is between 3.8 and 5. If it’s above 5, it’s bad. A pH level above 5 means the air is alkaline, which is good for bacterial vaginosis bacteria.
• Positive Whiff Test: When the vaginal fluid is mixed with 10% potassium hydroxide (KOH), the test is positive. A fishy smell from volatile amines made by bacteria means things will go well.
• Presence of Clue Cells on Microscopic Examination: Vaginal epithelial cells that are covered in bacteria are hint cells. Bacteria make the surface of cells rough or stippled, which makes it hard to see the edges of cells. Bacterial vaginosis is shown by finding clue cells.