Detection of Giardia lamblia antigen in the feces by counterimmunoelectrophoresis.

The presence of Giardia lamblia antigen in stools of symptomatic and asymptomatic giardiasis patients was studied by counterimmunoelectrophoresis using anti-G. lamblia (Portland strain I) trophozoite antibodies. This test could detect antigen in feces of 94% of giardiasis patients. However, it failed to differentiate between symptomatic and asymptomatic Giardia infection. There were no false-positive results in children with other diseases. Antigen in the stools disappeared within 1 to 2 weeks after eradication of infection with specific treatment. The overall sensitivity of this test in detecting G. lamblia antigen in stool was 94%, and the specificity was 95%.