Clinical and Interpretive

This assay is used in screening for the detection of Giardia antigens present in stool specimens.

Giardia lamblia are flagellated protozoa which can be found contaminating natural streams, lakes, and surface water municipal reservoirs. The human host ingests them in water, food, and by the fecal-oral route.

Giardia infect primarily the small intestine causing diarrhea by unknown mechanisms after attaching by their ventral sucker. Malabsorption may also occur.

Giardiasis is the most common intestinal parasitic infection in the United States and is a common cause of diarrhea in children (especially in day care centers), travelers, and in waterborne epidermics.

A positive enzyme-linked immunosorbent assay (ELISA) indicates the presence in a stool specimen of Giardia lambliaantigens.The assay has a sensitivity of 96%, specificity of 97%, and a positive predictive value of 95%.

Interpretation of results should be correlated with patient symptoms and clinical picture.

Small numbers of Giardia residing only in the duodenum may not yield a positive enzyme-linked immunosorbent assay (ELISA).

Giardia antigen detection should be used as an aid in diagnosis of giardiasis. A single diagnostic assay should not be used as the only criteria to form a clinical conclusion.

Testing of 3 consecutive stool specimens is recommended before considering the results negative.