Detection of Giardia antigen in stool samples before and after treatment.

A double antibody sandwich ELISA technique, using a chromatography purified Giardia antiserum, was applied to detect faecal antigen in patients infected with Giardia lamblia before and after treatment. The assay could detect antigens in 98% of infected cases with false positive reactions in 3 cases infected with E. histolytica. There was a significant direct relation between the antigen level in stool samples and the number of Giardia cysts. The mean level of copro-antigen was slightly lower in children, below 10 years, than in older patients, without significant difference. On the other hand, the lowest cyst count was noticed in elder patients, over 20 years. The level of faecal antigens decreased significantly after successful treatment in patients with giardiasis. It was concluded that detection of Giardia antigens by ELISA technique in the stool samples was a highly sensitive (98%) and specific (91%) diagnostic method. It is also considered as a good monitor for treatment success.