Latex agglutination test (LAT) for antigen detection in the cystic fluid for the diagnosis of cystic echinococcosis.

Latex agglutination test (LAT) was standardized and evaluated to detect hydatid antigen in fluid samples aspirated from 6 surgically proved human cases of cystic echinococcosis (CE), 4 suspected human cases of CE (2 cases of cysts in the liver which were not confirmed surgically and 2 cases of pelvic cysts later confirmed as abscesses) and 7 cases of hydatid cysts of liver in cattle. Echinococcus granulosus scolices and hook lets were seen in aspirated fluid by microscopy and the characteristic germinal layer of the cyst wall was demonstrated by histopathology in 6 human hydatid cysts operated and removed by surgery. In case of cattle hydatid liver cysts no scolices or hook lets were seen in aspirated fluid as they were sterile cysts but characteristic laminated layer of the cyst wall was demonstrated by histopathology of these cysts. The LAT could detect antigen in fluid samples collected from all 6 human cases of surgically proved CE and 7 cases of hydatid cyst liver in cattle, thus showing sensitivity of 100%. The LAT could detect antigen in fluid samples collected from 2 suspected cases of CE liver in humans, which were not operated. The LAT was found to be specific. No cross reactivity was observed. The results of the study showed that LAT could be employed as a simple and rapid diagnostic procedure, as an alternate to microscopy, to confirm the hydatid etiology of a suspected cyst.