SENSITIVITY OF MICROSCOPY VERSUS ENZYME-IMMUNOASSAY IN THE LABORATORYDIAGNOSIS OF GIARDIASIS

The substitution of enzyme immunoassay (EIA) techniques for microscopy as a screening tool for Giardia lamblia infection was assessed, Paire d stool samples obtained within a ten-day period from 366 patients wit h persistent diarrhea were examined by microscopy. In addition, two co mmercially available Giardia lamblia-specific EIAs were performed, Com pared with microscopy, EIA for copro-antigen detection was more sensit ive, based on examination of either one or two stool samples, Repeated examinations increased the number of cases detected, more so for micr oscopy than EIA, The negative predictive values of the two EIAs perfor med on the first stool sample were 98.7% and 97.8%. The results show t hat EIA for detection of copro-antigens in a single stool sample may b e almost as sensitive for identifying Giardia infection as repeated mi croscopy on two sequential stool samples.