Screening for Giardia/Cryptosporidium Infections Using an Enzyme Immunoassay in a Centralized Regional Microbiology Laboratory

Abstract

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