Describe the proper procedure for preparing a slide for KOH testing

Describe the proper procedure for preparing a slide for KOH testing. What steos ensure accurate results?

The correct answer and explanation is:

To prepare a slide for KOH (potassium hydroxide) testing, commonly used to differentiate fungal infections from bacterial infections, the following procedure should be followed:

1. Prepare the Slide: Start with a clean glass microscope slide. Use a tissue or a paper towel to wipe the surface of the slide and ensure no contaminants remain.
2. Place the Sample: Place a small amount of the specimen on the center of the slide. This can be a skin scraping, nail clipping, hair, or other suspected infection material. Use a sterile scalpel or swab to collect the sample from the patient.
3. Add KOH Solution: Using a dropper, place a few drops of 10-20% KOH solution directly on top of the specimen. KOH dissolves human cells and debris, leaving fungal elements such as hyphae, spores, or conidia intact for observation.
4. Cover with a Cover Slip: Gently place a cover slip over the specimen and KOH solution. Ensure there are no air bubbles trapped between the slide and cover slip.
5. Heat (Optional): If necessary, gently heat the slide by passing it over a flame for a few seconds. This helps to speed up the KOH’s action in dissolving tissue and debris, making the fungal elements more visible. However, overheating should be avoided to prevent distortion of the sample.
6. Examine the Slide: Place the slide on the microscope stage and begin examining it under low power (10x) to locate the sample. Then, switch to high power (40x or 100x) for detailed examination. Look for fungal elements such as hyphal structures, conidia, or budding yeast cells.
7. Document Results: If fungal elements are observed, document the findings, noting the shape and structure of the organisms. Record the absence of fungal elements if no structures are visible.

Key Considerations for Accurate Results:

• Ensure proper specimen collection and handling to avoid contamination.
• Use fresh KOH solution, as its strength may degrade over time.
• Avoid excessive heating, which could distort the fungal structures.
• Properly focus under the microscope to avoid missing small or faint fungal elements.

Following these steps ensures accurate results in diagnosing fungal infections using the KOH test.