Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1406 page)

PINWORM EXAMINATION

   Definition

   This test should be considered in patients, most often children, who present with pruritus ani. Sleep disturbances are common.

   Use

   This test is used to diagnose enteric infection with the parasitic pathogen
Enterobius vermicularis
(pinworm). Eggs or adult female worms are identified in specimens collected from skin of the perianal area. Specimens are collected with clear cellophane tape or a commercial pinworm collection device. The sticky side of the tape or collection device is pressed onto the perianal skin. Because the female worm emerges from the anus to lay eggs during the night, specimens should be collected in the early morning, before the patient passes a bowel movement, and ideally before arising.

   
Turnaround time:
24–48 hours.

   Interpretation

   
Expected results:
Negative.

   
Positive results:
Typical ova of
E
.
vermicularis
are usually seen. An adult female
E
.
vermicularis
, identified by characteristic structures, is occasionally seen.

   Limitations

   The sensitivity of a single examination is fairly low. The examination of multiple specimens is typically required for diagnosis; empirical treatment for enterobiasis may be a cost-effective alternative to therapy based on specific diagnosis.

   
Common pitfall:
The examination of only one or two specimens will often result in a false-negative diagnosis.

PNEUMOCYSTIS JIROVECII
(FORMERLY
PNEUMOCYSTIS CARINII
), MICROSCOPIC DETECTION

   Definition

   
Pneumocystis jirovecii
, a fungal pathogen, is ubiquitous in nature, with low pathogenic potential. In severely immunocompromised patients, especially patients with AIDS, however, it is responsible for potentially fatal respiratory disease.