Diagnosis of giardiasis by two methods. Immunofluorescence and enzyme-linked immunosorbent assay.

Antibody response in giardiasis was measured by indirect fluorescent antibody (IFA) and enzyme-linked immunosorbent assays (ELISA) on serum samples of 125 patients. Twenty-nine of these patients had symptomatic giardiasis; 30 were asymptomatic (carriers); 40 had other parasitic infections; 16 had inflammatory bowel diseases; ten were normal subjects. It was found that those patients with symptomatic giardiasis had higher IFA titers compared with all patients who did not have giardiasis and patients who had asymptomatic giardiasis. Serum samples with titers of 1:64 or greater in Giardia IFA were absorbed with Giardia and other parasite antigens. Only absorption with Giardia caused the titers to fall significantly. The ELISA technique was less specific than the IFA technique. Giardiasis elicits a specific host antibody response that may be used as an adjunct in its diagnosis.