Detection of hydatid antigen by co-agglutination in fluid samples from hydatid cysts.

The co-agglutination (Co-A) procedure was standardized and evaluated to detect hydatid antigen in fluid samples aspirated from hydatid cysts. Samples were collected from 14 hydatid cysts in different organs (liver, 7; lung, 5; multiple abdominal cysts, 1; and kidney, 1) by surgery. Echinococcus granulosus scolices and hooklets were seen in only 6 (42.85%) samples by routine microscopy. In contrast, hydatid antigen was demonstrated in all the samples by Co-A (100% sensitivity). Co-A could be employed as a simple and rapid diagnostic procedure, as an alternative to microscopy, to confirm the hydatid aetiology of a suspected cyst.