Diagnosis of giardiasis by counterimmunoelectrophoresis of feces.

The diagnosis of giardiasis is frequently difficult. In the present study, the techniques of microscopic examination of feces, duodenal fluid, and duodenal biopsy specimens were compared with counterimmunoelectrophoresis (CIE) of feces for Giardia lamblia antigen. New Zealand white rabbits were immunized with purified G. lamblia cysts and axial trophozoites, and the resulting antiserum was used for the detection of antigen. Of 276 patients with acute and chronic diarrhea studied using standard diagnostic methods, 66 patients had giardiasis: 62 by examination of feces; three, of duodenal fluid, and one, of duodenal biopsy specimens. CIE tests for G. lamblia fecal antigen had positive results for 65 of the 66 patients. The CIE test for Giardia fecal antigen appears to be as sensitive and reliable as the combined examination of feces and duodenal fluid.