Scotch tape (cellophane) test for pinworm

Principle

• The adult female Enterobius vermicularis migrates to the perianal skin at night to lay eggs.
• Eggs are collected from the skin on adhesive tape and seen under the microscope; stool examination detects them poorly.

Specimen

• Perianal specimen collected in the early morning, before bathing or defecation.

Reagents and equipment

• Clear (not frosted) cellophane tape, tongue depressor or commercial paddle, glass slide, gloves; optional toluene or xylene for clearing.

Procedure

• Loop the tape sticky side out over the end of a tongue depressor.
• Spread the buttocks and press the tape firmly against the perianal folds on several sides.
• Lay the tape sticky side down on a slide and smooth it; label with patient details.
• Optionally lift the tape and add a drop of toluene or xylene to clear, then press down again.
• Scan the whole tape with the 10× objective under reduced light; confirm with 40×.

Results

• Eggs: oval, flattened on one side (D-shaped), about 50–60 × 20–30 µm, thin smooth colorless shell, often with a developing larva inside.
• Adult female worms (about 8–13 mm, pointed tail) may also be seen on tape or skin.

Quality control and pitfalls

• A single negative tape does not exclude infection; test on at least 3 consecutive mornings.
• Collecting after bathing or defecation lowers yield.
• Eggs become infective within hours and are highly contagious; wear gloves and handle as infectious.
• Frosted tape makes eggs hard to see.

Clinical use

• Diagnosis of enterobiasis, especially in children with perianal itching (worse at night); family members are often tested and treated together.