The Wet Prep, also known as a Wet Mount, is a rapid diagnostic test performed in a clinical setting to identify the cause of common vaginal symptoms. This procedure involves collecting a small sample of vaginal discharge and examining it immediately under a microscope. The test quickly diagnoses the most frequent causes of vaginitis (inflammation of the vagina). Analyzing the sample allows healthcare providers to distinguish between bacterial, fungal, and parasitic infections, enabling prompt and targeted treatment.
What the Wet Prep Test Analyzes
Interpreting a wet prep result relies on three distinct analyses performed on the collected vaginal sample. The first step involves measuring the vaginal pH, an important indicator of the vaginal environment. A healthy pH is typically acidic, but an elevated level suggests the presence of certain types of infections.
The second component is the Saline Mount, where discharge is mixed with a saltwater solution and viewed under a microscope. This preparation allows for the identification of various cellular components, including epithelial cells, white blood cells, and any motile organisms. Observing these elements provides immediate clues about the underlying cause of the symptoms.
The third part of the analysis uses the Potassium Hydroxide (KOH) Mount, where the sample is mixed with a 10% KOH solution. This chemical dissolves most cellular material (like epithelial cells and bacteria) but leaves fungal structures intact, making yeast and their characteristic filaments easier to see. The KOH test also includes the “whiff test,” where the clinician checks for a strong, fishy (amine) odor, a specific indicator for certain bacterial overgrowths.
Interpreting Results for Specific Infections
The specific microscopic findings and chemical reactions observed during the wet prep are used to diagnose the three most common causes of vaginitis. Each condition presents with a distinct pattern.
Bacterial Vaginosis (BV)
Bacterial Vaginosis is indicated by a characteristic set of findings, most notably the presence of “clue cells” on the saline mount. Clue cells are vaginal epithelial cells covered in rod-shaped bacteria, giving the cell edges a stippled appearance. The vaginal pH is typically elevated above 4.5 due to the shift away from acid-producing bacteria. A strong, fishy odor upon the addition of KOH (the positive “whiff test”) further supports a BV diagnosis.
Candidiasis (Yeast Infection)
Candidiasis (Yeast Infection) is primarily diagnosed by identifying fungal structures on the KOH mount. Defining features are pseudohyphae (long, branching filaments) and budding yeast forms (small, oval shapes). Unlike bacterial infections, the vaginal pH is usually within the normal, acidic range (typically 4.5 or lower). The “whiff test” is negative, as the chemical reaction producing the fishy odor does not occur with a fungal overgrowth.
Trichomoniasis (Trich)
Trichomoniasis (Trich), a sexually transmitted infection, is confirmed by visualizing the Trichomonas vaginalis protozoan on the saline mount. These organisms are slightly larger than white blood cells and are recognized by their rapid, jerky, twisting motility. Diagnosis must be made quickly, as these organisms lose motility soon after the sample is collected. Like BV, the vaginal pH is often elevated (ranging between 5.0 and 7.0), and a positive “whiff test” may be present due to the associated change in bacterial flora.
Understanding Normal Findings and Next Steps
A normal wet prep result is defined by findings that indicate a balanced vaginal environment. The vaginal pH should be acidic, typically 4.5 or less. Microscopic examination should reveal a dominance of Lactobacilli, large, rod-shaped bacteria responsible for maintaining the low pH.
A normal result shows an absence of specific infection markers, such as clue cells, motile trichomonads, and yeast forms. The ratio of white blood cells to epithelial cells should be low (usually around 1:1), indicating no significant inflammation. If the test is normal but symptoms persist, a healthcare provider may need to explore other causes of irritation the wet prep does not detect.
If the wet prep is abnormal and identifies one of the common infections, the next step is to consult a healthcare professional for appropriate treatment. The rapid nature of the test allows for immediate prescription of medication tailored to the specific pathogen identified. While informative, a complete diagnosis also considers the patient’s symptoms and medical history.