infectious diseases
Pinworm Infestation
Diagnosis of Pinworm Infestation
Examination of the perianal region for worms, ova, or both Pinworm infestation can be diagnosed by finding the female worm, which is 8 to 13 mm long (males are 2 to 5 mm), in the perianal region 1 or 2 hours after a child goes to bed at night or in the morning or by using a low-power microscope to identify ova on cellophane tape. Samples are obtained in the early morning before the child arises by patting the perianal skinfolds with a strip of cellophane tape, which is then placed sticky side down on a glass slide and viewed microscopically. The 50- by 30-micron ova are oval with a thin shell that contains a curled-up larva. A drop of toluene placed between tape and slide dissolves the adhesive and eliminates air bubbles under the tape, which can hamper identification of the ova. This procedure should be repeated on 3 successive mornings if necessary. On occasion, the diagnosis can be made by examining samples taken from under the patient's fingernails. Eggs may also be encountered, but less frequently, in stool, urine, or vaginal smears. 