Setting up a wet prep, also known as a wet mount, is a fundamental and rapid diagnostic technique used to examine fresh clinical specimens, often vaginal discharge, under a microscope. This method allows for the immediate visualization of various microorganisms like yeast, Trichomonas vaginalis, and clue cells associated with bacterial vaginosis, aiding in quick diagnosis and treatment.
What is a Wet Prep?
A wet prep involves mixing a small amount of a patient's specimen with a diluent, typically saline, on a microscopic slide. This preparation is then covered with a coverslip and observed directly under a light microscope. Its simplicity and speed make it an invaluable tool in many clinical settings, particularly for conditions requiring immediate assessment.
Essential Materials for Wet Prep Setup
To perform a wet prep effectively, you will need the following materials:
- Specimen Collection Swab: Dacron, wooden, or cotton swabs are commonly used for collecting samples.
- Specimen Transport Tube: A Red Top tube containing 1 ml of saline. This volume is usually sufficient to cover the tip of the swab.
- Microscope Slides: Clean, standard glass slides.
- Coverslips: Small, thin pieces of glass or plastic that cover the specimen on the slide.
- Saline Solution (0.9% NaCl): Used as a diluent.
- Dropper or Pipette: For dispensing saline and the specimen.
- Gloves: Essential for infection control.
- Microscope: A compound light microscope with various magnifications (e.g., 10x, 40x).
- Timer (Optional): For consistent observation times if required by protocol.
Step-by-Step Guide to Setting Up a Wet Prep
Follow these steps to correctly prepare a wet mount for microscopic examination:
1. Specimen Collection and Transport
The quality of your wet prep begins with proper specimen collection.
- Collect the Specimen: Using a Dacron, wooden, or cotton swab, carefully collect the clinical specimen (e.g., vaginal discharge).
- Prepare for Transport: Immediately after collection, place the swab into a Red Top tube that contains approximately 1 ml of saline. Ensure the saline fully covers the tip of the swab.
- Seal and Label: Securely seal the cap of the tube. Crucially, label the tube immediately with the full patient name, date of birth, and the precise collection date and time. This prevents misidentification and ensures accurate patient care.
2. Slide Preparation
Once the specimen is ready, proceed to prepare the microscopic slide.
- Prepare Your Workspace: Don gloves and ensure your work area is clean and organized.
- Aliquot Specimen: Gently remove the swab from the transport tube. Roll or swirl the swab well in the saline to release the specimen into the liquid. You can also gently press the swab against the side of the tube to express fluid.
- Apply to Slide: Using a dropper or pipette, place one small drop of the saline-specimen mixture onto the center of a clean microscope slide.
- Tip: Avoid using too much liquid, as it can cause the coverslip to float and the specimen to drift.
- Add Coverslip: Carefully lower a coverslip over the specimen drop. Start by placing one edge of the coverslip down first and then slowly drop the rest, allowing it to settle without trapping air bubbles. This helps to create an even layer of fluid.
3. Microscopic Examination
With the slide prepared, it's time to examine it under the microscope.
- Initial Scan (Low Power - 10x):
- Place the slide on the microscope stage.
- Start with the 10x objective lens (low power).
- Adjust the light and focus to get a clear view.
- Systematically scan the entire field to get an overall impression of cellularity, presence of epithelial cells, white blood cells, and any large structures.
- Detailed Examination (High Power - 40x):
- Once you've scanned at 10x, switch to the 40x objective lens (high power) to examine specific areas of interest in greater detail.
- Refocus carefully.
- At 40x, you can identify:
- Trichomonads: Look for motile, flagellated organisms, typically slightly larger than white blood cells. Their characteristic jerky motility is a key diagnostic feature. Learn more about Trichomonas vaginalis from the CDC.
- Yeast (Candida): Observe budding yeast forms and possibly pseudohyphae. They often appear as oval structures.
- Clue Cells: These are vaginal epithelial cells completely covered with small, pleomorphic bacteria, making the cell borders indistinct or "shaggy." They are a hallmark of bacterial vaginosis.
- White Blood Cells (WBCs): Note their presence and quantity, as an increased number can indicate inflammation.
- Epithelial Cells: Squamous epithelial cells are normal inhabitants of vaginal secretions.
Key Considerations for Quality Results
- Fresh Specimen: Examine the wet prep as soon as possible after collection, ideally within 30 minutes, especially when looking for motile organisms like Trichomonas.
- Proper Lighting: Adjust the condenser and diaphragm on your microscope to achieve optimal contrast. Too much light can make translucent organisms difficult to see.
- Systematic Scan: Always scan the entire area under the coverslip to avoid missing important findings.
- Magnification Use: Start at lower power to orient yourself and then move to higher power for detailed identification.
Common Wet Prep Findings
| Finding | Appearance | Associated Condition |
|---|---|---|
| Trichomonads | Pear-shaped, flagellated, motile organisms (jerky movement), slightly larger than WBCs | Trichomoniasis |
| Yeast | Oval, budding forms; may see pseudohyphae (branching structures) | Candidiasis (Yeast Infection) |
| Clue Cells | Vaginal epithelial cells coated with bacteria, obscuring cell borders | Bacterial Vaginosis |
| WBCs | Round cells with granular cytoplasm and multi-lobed nuclei (neutrophils) | Inflammation, infection |
| Epithelial Cells | Large, flat, irregularly shaped cells with central nucleus | Normal (squamous epithelial cells) |
By following these guidelines, you can accurately set up and interpret a wet prep, contributing to timely and effective patient care. For more information on microscopic examination techniques, resources like Lab Tests Online can provide additional context.
