The wet prep test is a common, rapid diagnostic procedure frequently used in gynecology to investigate symptoms such as abnormal discharge, itching, or irritation. It is a form of microscopy that provides a quick look at the cellular and microbial environment of the vagina. Understanding the technical terms on the report can be challenging, but clarifying this terminology is essential for understanding a diagnosis. This article will explain the process of the wet prep test and clarify the meaning of the various findings, from a healthy result to the specific markers of infection.
What is the Wet Prep Test?
The wet prep test, also known as a wet mount, begins with a healthcare provider collecting a sample of vaginal discharge using a sterile swab. This sample is then prepared on a glass slide in two primary ways for immediate microscopic analysis. One portion of the sample is mixed with a drop of 0.9% saline solution to create a saline wet mount, which preserves the cell structures and allows for the observation of motile organisms.
A second preparation is often made by adding a drop of 10% potassium hydroxide (KOH) to a different portion of the discharge. The strong alkaline nature of KOH helps to dissolve epithelial and bacterial cells, which makes it much easier to visualize fungal elements. Analyzing both the saline and KOH preparations under a microscope permits the identification of specific microscopic elements, including different types of cells, bacteria, and other microorganisms.
Interpreting Normal Findings
A healthy wet prep report indicates a balanced vaginal ecosystem. The primary cells expected to be seen are squamous epithelial cells, which are the large, flat cells shed from the vaginal wall. These cells should appear with distinct, smooth borders and dominate the microscopic field.
The presence of Lactobacilli, which are large, rod-shaped bacteria, is also expected. These organisms are the hallmark of a healthy vaginal environment, as they produce lactic acid, maintaining the acidic pH. A normal vaginal pH reading is typically 4.5 or lower, often falling within the 3.8 to 4.2 range. Finally, a normal result will show only a small number of white blood cells (WBCs), indicating an absence of significant inflammation or infection.
Understanding the Key Abnormal Results
The presence of specific microscopic elements often points directly to one of the three most common causes of vaginitis, which are Bacterial Vaginosis, Candidiasis, and Trichomoniasis.
Bacterial Vaginosis (BV)
Bacterial Vaginosis is characterized on a wet prep report by the finding of clue cells. These are vaginal epithelial cells that appear stippled or granulated because their surfaces are heavily coated with a dense layer of coccobacilli bacteria. The adherence of the bacteria obscures the typically sharp, defined edges of the epithelial cell. The presence of clue cells, especially when they make up more than 20% of the observed epithelial cells, is a strong indicator of BV. This condition is also associated with an elevated vaginal pH, usually measuring greater than 4.5, due to the shift away from Lactobacilli.
Candidiasis (Yeast Infection)
A yeast infection, or Candidiasis, is indicated by the visualization of specific fungal forms. The report may note the presence of budding yeast, which are small, oval structures representing the single-celled form of the fungus. A more definitive sign is the observation of hyphae or pseudohyphae.
Hyphae are long, branching, filamentous structures that represent the invasive, multi-celled growth pattern of the fungus. Pseudohyphae are similar, but they appear as a chain of elongated yeast cells that have constrictions at the junctions between cells. These fungal elements are often seen more clearly on the KOH preparation, as the solution clears away other cellular debris, allowing the distinct fungal cell walls to stand out. Unlike BV, Candidiasis typically does not alter the normal acidic vaginal pH.
Trichomoniasis
The diagnosis of Trichomoniasis, a sexually transmitted infection, is made by identifying the Trichomonas vaginalis organism itself. The report will describe these as motile trichomonads or flagellated protozoa. These are small, pear-shaped organisms, roughly the size of a white blood cell, that possess several whip-like flagella.
The most distinguishing feature under the microscope is their characteristic, erratic, and jerky movement, which is best observed immediately after the sample is collected and prepared. If the organism is not motile, it can be difficult to differentiate it from other cell types. Like BV, a Trichomoniasis infection often raises the vaginal pH, sometimes to levels above 5.0 or 6.0, and often shows a significant increase in white blood cells due to the inflammatory nature of the infection.
Next Steps After Diagnosis
Receiving a positive result for an infection requires a prompt discussion with your healthcare provider to initiate appropriate therapy. For Bacterial Vaginosis and Trichomoniasis, the standard treatment often involves oral antibiotics, such as metronidazole or tinidazole. It is important to complete the entire course of medication prescribed, even if symptoms begin to improve quickly, to ensure the infection is fully eradicated and to minimize the risk of recurrence.
Candidiasis is typically treated with either topical antifungal creams or a single dose of an oral antifungal medication, such as fluconazole. For Trichomoniasis, treatment is necessary for all sexual partners, regardless of whether they show symptoms, to prevent reinfection. Follow-up testing may be recommended, particularly if symptoms persist after treatment, to confirm that the infection has cleared successfully and the vaginal flora has returned to a healthy state.