The clear-cellulose tape preparation is the most widely used procedure for the detection of human pinworm infections.
Adult Enterobius vermicularis worms inhabit the large intestine and rectum; however, the eggs are not normally found in fecal material. During period of extraintestinal migration, the adult female migrates out the anal opening and deposits the eggs on the perianal skin, usually during the night.
The eggs, and occasionally the adult female worms stick to the glued (sticky) surface of the cellulose tape. These cellulose tape preparations are submitted to the laboratory, where they are examined under microscope. Commercial collection systems ‘pinworm paddles’ are also available.
Time of specimen collection
The specimen is collected from the perianal skin. An early-morning sample, before the patient has bathed, or used the toilet, is optimal. Up to six successive day morning samples should be collected before a negative result is issued.
- Place a strip of clear cellulose tape (adhesive side down) on a microscope slide as follows: Starting ca. 1.5 cm from one end, run the tape toward the same end, and wrap the tape around the slide to the opposite end. Tear the tape even with end of the slide. Attach a label to the tape at the end torn flush with the slide.
- To obtain a sample from the perianal area, peel back the tape by gripping the labeled end, and, with the tape looped (adhesive side outward) over a wooden tongue depressor that is held firmly against the slide and extended about 2.5 cm beyond it, press the tape firmly several times against the right and left perianal folds.
- Smooth the tape back on the slide, adhesive side down.
- Label with patient name and date.
- Submit the tapes and slides to the laboratory in a plastic bag.
- Once the sample is obtained, remove the slide from the tongue depressor and affix the tape sticky side down on the glass slide.
- Label the slide with the patient name and date of collection
- Examine the slide under a microscope using the low power (10x) objective. The eggs can be made more visible by detaching the tape from the slide, adding a drop of xylene or toluene, and again affixing the tape.
- The eggs of E.vermicularis measure 50-60 micrometer x 20-30 micrometer and have a relatively thick, smooth shell and an ovoid shape flattened on one side, much like a flattened, partially inflated football. It may contain a partially or fully developed larva.
- Adult worms occasionally are seen in transparency tape preparations. The measure 1 cm long, have a pointed tail posteriorly and transparent wings flanking the anterior end.
A. Report her organism and stage. Do not use abbreviations.
Example: Enterobius vermicularis eggs present.
B. Report adult worms.
Example: Enterobius vermicularis adult worm present.
C. Report negatives.
Example: No Enterobius vermicularis eggs or adults seen.
- The eggs of E. vermicularis are infectious if swallowed, so the person obtaining specimen must wear the gloves.
- If opaque tape is submitted by mistake, a drop of immersion oil on the top of the tape will clear it enough to proceed with the microscope examination.
Limitations of the test-cellulose tape preparation for pinworm examination
- The female pinworm deposits eggs on the perianal skin only sporadically.
- Without multiple tapes (taken on consecutive morning), it is not possible to determine if the patient is positive, or negative for the infection