Journal of Immunological Methods, 137 (1991) 245-251 © 1991 Elsevier Science Publishers B.V. 0022-1759/91/$03.50 ADONIS 0022175991001152 245 JIM 05863 An immunoenzymatic dot-ELISA for the detection of Giardia lamblia antigen in stool eluates of clinical cases of giardiasis V.K. Vinayak, Parmesh Dutt and Munish Puff Department of Experimental Medicine, PostgraduateInstitute of Medical Education and Research, Chandigarh, India (Received 5 June 1990, revised received 8 October 1990, accepted 26 November 1990) A dot-ELISA technique for the detection of G. lamblia specific antigen in stool eluates of clinical cases of giardiasis was developed and evaluated employing monospecific antibodies to a G. lamblia specific coproantigen with a molecular mass of 66 kDa. The assay detected 22 (91.7%) of the 24 microscopically confirmed cases of giardiasis while none of the stool eluates from 20 patients with gastrointestinal parasites other than G. lamblia and 20 apparently healthy subjects had any detectable levels of G. lamblia-specific coproantigen. Of the 25 stool eluates from clinically suspected cases of giardiasis, 13 (52%) were found to contain G. lamblia-specific coproantigen. A 3-month-follow up of five of such cases where stool eluates has antigen detected by dot-ELISA assay, revealed the presence of G. lamblia cysts on repeated stool examinations. All the clinically suspected cases with detectable levels of G. lamblia-specific coproantigen by dot-ELISA were relieved of their clinical symptoms following metronidazole therapy. Single stool eluate examination by dot-ELISA was found to be sufficient to confirm the diagnosis. The dot-ELISA is an easy, rapid, sensitive and specific procedure for confirming the diagnosis of suspected cases of giardiasis. It should be a valuable diagnostic aid under field conditions as well as in the laboratory. Key words: Giardia lamblia; Copromatigen; ELISA, dot- Introduction Giardiasis, a flagellate protozoan infection of the small bowel, has come into prominance during the last decade or so because of increasing aware- ness that it results in a high degree of morbidity Correspondence to: V.K. Vinayak, Department of Experi- mental Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh - 160 012, India. Abbreviations: ME, microscopic examination; CIEP, coun- terimmunoelectrophoresis; ELISA, enzyme-linked immuno- sorbent assay; SD, standard deviation; HRP, horseradish per- oxidase; NCP, nitrocellulose paper. and loss of manpower. The laboratory diagnosis of giardiasis conventionally depends on the dem- onstration of cystic or trophic forms of the para- site, Giardia lamblia, in stool samples from clini- cally suspected cases. In as many as 50% of such cases, the cystic or the trophic forms of G. lamblia cannot be demonstrated by single stool examina- tion (Burke, 1975, 1977) and confirmation of giardiasis may require several stool examinations. Examination of duodenal aspirates or a biopsy from the duodenum for the presence of tropho- zoites may provide confirmation of the diagnosis in a few more cases (Naik et al., 1978; Thornton et al., 1983) but the detection of serum antibodies in