A specific test for the identification of cyst fluid samples from suspected human hydatid infections.

A simple and sensitive two-step enzyme immunoassay for Echinococcus antigen was developed, using peroxidase conjugated IgG fractions of rabbit anti-Echinococcus granulosus cyst fluid serum or of pooled sera from human hydatid patients, to assay samples of cystic fluid taken from patients with suspected hydatid cyst infections. The assay was 100% positive with nine proven human hydatid cyst fluids; in six patients with cysts where serology was negative, there was no evidence of Echinococcus antigen in the cyst fluid. This simple procedure is therefore of value in confirming or excluding the diagnosis of hydatid in cystic fluid obtained by biopsy or after surgery.