Enterobius (Pinworm) - Microscopy

Consistent with O. Reg. 671/92 of the French Language Services Act, laboratory testing information on this page is only available in English because it is scientific or technical in nature and is for use only by qualified health care providers and not by members of the public.

Background
This page provides microscopy testing information for enterobiasis at Public Health Ontario (PHO). The causative agent of enterobiasis, also known as pinworm infection or oxyuriasis, is the parasitic nematode Enterobius vermicularis.

Updates
This webpage has been updated to include background, testing indications, acceptance criteria, performance and limitations, interpretations, and expected turnaround times based on calendar days instead of business days.

*Uncontrolled print copy. Valid only on day of print: 18 Dec 2025.

Testing Indications

Microscopic examination of four to six daily specimens collected from perianal skin is recommended for individuals with clinical symptoms (e.g. perianal pruritus) and/or epidemiologic risk factors (household contact) suggestive of pinworm infection. The two most used collection methods are:

Use of clear adhesive cellulose tape or commonly referred to as “tape test”
Use of plastic paddle devices (“Swube tube”)

Stool samples are NOT recommended due to their limited sensitivity (under 10%); multiple specimens collected from the perianal skin should be collected instead.

Note: There are currently no PCR or serological tests available at PHO for Enterobius.

Acceptance/Rejection Criteria

Testing will only be accepted in cases with any of the following documented on the requisition:

Signs or symptoms consistent with pinworm infection (e.g. perianal itching or pruritus ani)
Close contact exposure with infected individual

Note: Only one specimen per patient per collection date will be tested. Any additional specimens collected on the same date will not be tested. If submitting multiple specimens, ensure each is collected at least 1 to 2 days apart for them to be eligible for testing.

Specimen Collection and Handling

Specimen Requirements

Test Requested

Required Requisition(s)

Specimen Type

Minimum Volume

Collection Kit

Enterobius or Pinworm – Microscopy

General Test Requisition

Adhesive cellulose tape

Adhesive plastic paddle

As per kit instructions (see below)

Pinworm Ova Kit order#390045

Submission and Collection Notes

Complete all fields of the requisition form.

Important: Specify any of the following testing indications on the requisition. Failure to provide this information may result in rejection:

Signs or symptoms compatible with pinworm infection
Close contact exposure with infected individual

For clinical specimens, label the specimen container(s) with the patient’s first and last name, date of collection, and one other unique identifier such as the patient’s date of birth or Health Card Number. For additional information see: Criteria for Acceptance of Patient Specimens. Failure to provide this information may result in rejection or testing delay.

Timing of Specimen Collection

Specimens should be collected daily for 4 to 6 consecutive days to rule out infection since female pinworms deposit eggs on the perianal skin only sporadically. Collection is best performed in the morning upon awakening and prior to defecation or washing of the perianal area.

Storage and Transport

After washing hands, place specimen container in a biohazard bag and properly seal the bag. Store at room temperature (or alternatively at 2-8°C) and ship to PHO within 48 hours of collection. All specimens must be shipped in accordance with the Transportation of Dangerous Good Act.

Special Instructions

The following steps should be performed per specimen:

Prepare for collection in the morning upon waking up and prior to defecation or washing of the perianal area.
Wash hands and ideally wear glove where feasible.
Press the sticky adhesive surface of the cellulose tape or plastic paddle against the perianal area with moderate pressure, using a rocking motion to cover as much of the perianal skin as possible.
Return the paddle into the vial.
Wash hands and securely screw the vial cap.

Repeat the same steps every day until four to six specimens are collected in total.

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

Microscopy is performed daily from Monday to Friday at PHO’s laboratory -Toronto, Peterborough, Ottawa, and London sites. Turnaround time is up to 7 calendar days from receipt at the laboratory.

Test Methods

Microscopy is performed at PHO directly on the adhesive portion of the collection device.

Performance and Limitations:
There is no reported difference in performance between the cellulose tape or paddle techniques.
The sensitivity of a single specimen microscopic examination is estimated at under 60%, therefore a negative result does not rule out infection. Sensitivity increases to 90% when three specimens are collected daily, and close to 100% when six specimens are collected daily.^1,2

Interpretation

Microscopy:

Parasitology – Pinworm	Interpretation
*Enterobius vermicularis* found.	The organism stage(s) will be reported. Assessment of close contacts (e.g. household members) for testing and/or treatment is recommended.
Enterobius vermicularis not found.	Due to low sensitivity, up to six total daily perianal samples are recommended for testing if clinically indicated.

Reporting

Results are reported to the physician, authorized health care provider (General O. Reg 45/22, s.18) or submitter as indicated on the requisition.

References

Cook GC. Enterobius vermicularis infection. Gut. 1994 Sep;35(9):1159-62. doi: 10.1136/gut.35.9.1159.
Sadun EH, Melvin DM. The probability of detecting infections with Enterobius vermicularis by successive examinations. J Pediatr. 1956 Apr;48(4):438-41.