Serological diagnosis and post-operative surveillance of human hydatid disease. II. The enzyme-linked immunosorbent assay (ELISA) using various antigens.

The ELISA using a urease conjugated antibody and 3 antigen preparations was examined for sensitivity and specificity in hydatid diagnosis. Four groups of sera tested were: 80 samples from patients with confirmed hydatid infection; 51 latex agglutination test (LA) +ve and immunoelectrophoresis test (IEP) -ve sera from patients with miscellaneous symptoms or disorders other than hydatid disease; 195 'normal' sera from healthy donors; 115 sera from persons infected with other parasites. Antigens tested included crude sheep hydatid cyst fluid (CSHCF), CSHCF partially purified by salt fractionation (PPSHCF) and CSHCF purified by sequential affinity chromatography depletion with rabbit anti-sheep IgG, 3EgH 29-2 anti-Echinococcus monoclonal antibody and 'normal' sheep Ig (ADSHCF). All 3 antigens showed high sensitivity in detecting antibody in serum from hydatid-infected patients, and gave excellent discrimination between these samples and the LA +ve IEP -ve sera and the 'normal' sera. Cross-reactions occurred with antibodies in the sera of patients with other parasitic infections, especially other larval cestodes and filarial parasites. Superior specificity was achieved with both CSHCF and ADSHCF, and ADSHCF reacted only with a single serum sample from an E. multilocularis patient. It was concluded that a combination of ELISA and IEP was useful for the diagnosis of hydatid disease, that ELISA at a single dilution could be useful as a screening test where other larval cestode infections were not prevalent and that ELISA was not of value for post-operative surveillance.