Evaluation of GiardEIA kit for giardiasis diagnosis

Giardia lamblia is recognized as one of the most common agents for diarrhea world wide. To date, microscopical examination of stool samples is the gold standard for giardiasis diagnosis. However, intermittence of the Giardia cycle and some medications may cause temporary disappearance of cysts from stools, thus giving false negative results. In the present study, we evaluated a commercially available enzyme immunoassay kit (GiardEIA) for the detection of Giardia copro-antigens and compared the results with those of the merthiolate-iodine-formaldehyde concentration (MIFC) microscopical examination technique. Sixty-nine fecal samples from children 2-12 years old were emulsified and allowed to react with a Giardia specific antibody, then with an enzyme conjugated antibody and the reaction was developed colorimetrically. Seventy-four percent of the parasitologically positive Giardia cases were also positive by GiardEIA while 26% of the microscopically negative cases were positive by the assay. GiardEIA gave negative results with 82% and 100% of stools with helminthic and protozoan (other than Giardia) infections, respectively. Similarly, no cross-reactivity was found with any of the bacterial agents including Shigella flexneri, pathogenic E. coli, Klebsiella spp. and Salmonella typhi. GiardEIA is a simple assay that can diagnose 24 samples in less than an hour without the need for any special equipment and can be useful in epidemiological surveys and in giardiasis outbreaks.