Perianal tape test

The perianal tape test detects infection with pinworm (Enterobius vermicularis), the most common intestinal parasite in children. A sample is collected using clear adhesive tape from the skin around the anus, in the morning before washing, and the laboratory looks for worm eggs under a microscope.

Who the test is for

• children and adults with itching of the skin around the anus, particularly at night;
• children who sleep restlessly, wake up and are irritable without another clear cause;
• girls with genital itching or redness;
• children and adults in whom small white thread-like strands have been noticed around the anus at night or on stools;
• household members of someone with confirmed pinworm, and children in the same nursery group, as recommended by a doctor.

What pinworm is and why a tape test is performed

Pinworm is a small white worm about one centimetre long that lives in the large intestine. Females emerge to the anus at night and lay eggs on the surrounding skin, causing itching. Scratching transfers the eggs onto fingers and under nails, and from there onto bedding, underwear, toys and food. Infection spreads by swallowing eggs, so it passes easily between children in nurseries and schools and between household members. Anyone can become infected, regardless of how carefully they maintain hygiene.

Because the eggs remain on the skin around the anus and are rarely present in stools, an ordinary stool test is insufficient to detect pinworm. The correct sample is an impression of the skin around the anus.

Many infected people have no symptoms, so pinworm is sometimes discovered only when other household members are tested.

Preparation and sample collection

You need a microscope slide and clear adhesive tape for the sample. The tape must be transparent, rather than cloudy or matt, so that the eggs can be seen under a microscope. Collect the sample as follows:

1. In the morning, immediately after waking and before washing, using the toilet or dressing, cut a piece of tape slightly shorter than the slide.
2. Spread the buttocks, with the child lying on their side or bending over. Press the sticky side of the tape several times against the skin around the anus, from several sides.
3. Stick the tape flat onto the slide, with the sticky side facing the glass, without folds or air bubbles.
4. Label the slide with the name and date, wrap it in soft paper or place it in a container to prevent breakage.
5. Wash your hands thoroughly with soap and warm water.

Females do not lay eggs every night, so one tape sample may not reveal infection. Collecting an impression on three consecutive mornings, each time on a new slide, is therefore recommended. Bring the samples to the laboratory as soon as possible after collection.

How to interpret the result

A positive result means that pinworm eggs were found on the tape and infection is confirmed. A paediatrician or family doctor prescribes medication. All household members are usually treated simultaneously, and the doctor often prescribes a second dose after two weeks, because the medicine does not destroy eggs. Alongside treatment, it is important to keep nails short, wash hands after using the toilet and before eating, shower in the morning, change underwear daily and wash pyjamas, bedding and towels at a high temperature.

A negative result from one tape sample does not rule out infection. If symptoms persist, your doctor will suggest tape samples on three consecutive mornings or repeating the test.

Perianal tape test or stool test?

For pinworm, the correct sample is a tape impression. If a child has diarrhoea, abdominal pain or bloating, a doctor may look for other intestinal parasites, such as Giardia, in stools. The test used for this is the stool for cysts and parasites and Intestinal parasite panel, which looks in stools for the pathogens Entamoeba histolytica, Giardia lamblia and Cryptosporidium parvum. The panel does not detect pinworm, so it does not replace the perianal tape test.

How to arrange testing

The test is available without a referral or appointment: you can hand in slides with the sample at any of our branches (list on the page Contact). Prices for all tests and panels are available in the service price list.

Frequently asked questions

Can pinworm be seen with the naked eye?

Sometimes. Adult worms look like small white threads about one centimetre long and are easiest to notice at night or early in the morning on the skin around the anus, and sometimes on stools. Eggs cannot be seen with the naked eye, which is why a tape impression is taken for detection.

Do all household members need treatment?

When pinworm is confirmed in one family member, a doctor usually recommends treating all household members at the same time, since those without symptoms are often infected too. This reduces the chance of reinfection.

Can you get pinworm from a dog or cat?

No. Pinworm lives only in humans and spreads from person to person, so pets do not need treatment for it.

Why is the result negative while the child keeps scratching?

Eggs are not present on the skin every morning, and a sample taken after washing or using the toilet may be falsely negative. Repeating the tape test on three consecutive mornings helps. Itching around the anus can have other causes too, such as irritated skin, so it is a good idea to show it to a doctor.