Screening for Giardia/Cryptosporidium infections using an enzyme immunoassay in a centralized regional microbiology laboratory.

Context: Stool parasitologic testing for Giardia and Cryptosporidium (G/C) previously relied on staining (ie, modified iron hematoxylin-kinyoun), ethyl acetate concentration procedures, and microscopy (the stool ova and parasite method). In April 1999, a microplate enzyme immunoassay (EIA) (ProSpecT G/C, Remel, Inc, Lenexa, Kan) for routine screening of all stool specimens was implemented.

Objective: To determine the clinical and laboratory impact of this service change.

Design: Changes were made to the regional microbiology requisition so that physicians could order either a G/ C EIA screen or stool ova and parasite examination. During a 3-year period (May 1999 through April 2002), changes in physician ordering practice, the rate of detection of G/ C infections, and test turnaround times were monitored. The economic outcomes have also been studied and compared annually since implementation and up to the current fiscal year (2004).

Results: The following effects have been noted since G/ C EIA screening was implemented: (1) 70% of all stool parasite tests ordered were converted to G/C EIA screens versus stool ova and parasite tests, (2) stool parasitologic volumes decreased by up to 30% because of physicians ordering a single test per patient, (3) most stool parasite results (70%-80%) were reported within 24 hours of specimen receipt, and (4) the screening assay has improved detection of cryptosporidiosis cases. Although the G/C EIA tests cost more than stool ova and parasite examination, the equivalent of 1.8 full-time employees have been freed up to perform other duties.

Conclusions: Routine stool G/C EIA screening in our region is not only clinically relevant but also improves the timeliness and efficiency of detection of these important enteric parasite infections.