How to Diagnose Pinworm (Enterobius vermicularis) Infection
The cellophane tape test (also called the Scotch tape test or sellotape test) performed on the perianal skin in the morning before bathing is the diagnostic method of choice for pinworm infection. 1, 2
Why the Tape Test is Preferred
- Stool examination is NOT recommended for pinworm diagnosis because eggs and adult worms are not typically passed in stool 1, 2
- The unique life cycle of pinworms explains why perianal sampling works: gravid female worms migrate to the perianal region at night to deposit eggs on the skin surface 1
- The tape test is specifically designed to capture these eggs deposited overnight on the perianal skin 1
How to Perform the Cellophane Tape Test
- Apply clear adhesive tape (cellophane/Scotch tape) to the perianal skin first thing in the morning before bathing or defecation 1, 3, 2
- Press the sticky side of the tape firmly against the perianal folds 2
- Transfer the tape to a glass slide for microscopic examination 2
Test Sensitivity and Repeat Testing
- A single tape test has only ~50% sensitivity, so negative results do not rule out infection 2
- Perform the test on three consecutive mornings to increase sensitivity to approximately 90% 2, 4
- In young girls with urinary tract infections, consider applying tape to both perianal AND perineal regions on at least three consecutive occasions 4
Clinical Clues That Support the Diagnosis
- Nocturnal perianal itching is the most common symptom and should prompt testing 5, 1, 3, 2
- However, 30-40% of infected children are completely asymptomatic 6, 2
- Other symptoms may include weight loss, irritability, diarrhea, abdominal pain, and occasionally colitis with eosinophilia 5, 1, 3
- In females, worms may enter the genital tract causing vulvovaginitis or vaginal discharge 5, 1, 3
Alternative Diagnostic Methods (When Available)
- Direct visualization: If a worm is seen in the perianal area or stool, pathological examination provides definitive diagnosis 2
- Nucleic acid amplification tests (NAAT) may be used when available but are not typically necessary for routine diagnosis 1
- Concentrated stool microscopy or fecal PCR can be performed but have poor sensitivity compared to the tape test 5
Common Pitfall to Avoid
The most critical error is relying on routine stool ova and parasite examination, which has poor sensitivity for pinworm detection because the eggs are deposited on perianal skin rather than passed in feces 1, 2.