Standardization and evaluation of an enzyme immunoassay as a screening test for the seroepidemiology of human hydatidosis.

The immunodiagnosis of human hydatidosis caused by Echinococcus granulosus is based on the detection of antibodies against arc 5 antigens by the double diffusion (DD5) or counterimmunoelectrophoresis (CIE5) tests. However, neither of those tests is practical for seroepidemiological surveys in which a great number of samples have to be processed. The present study was carried out to evaluate if a solid phase enzyme immunoassay (EIA) standardized to detect total antibodies against E. granulosus cyst fluid antigens would permit the selection of sera with antibody activity against arc 5 antigens detectable by DD5. Groups of sera representing 5 possible results with DD5 were studied by the EIA proposed as a screening test. Using the EIA all the sera with antibody activity against arc 5 antigens were differentiated from all those which did not produce any precipitation band in DD5. It was also possible to differentiate those with no antibodies from all those with antibodies against 3 non-arc 5 antigens, most with antibodies against 2 non-arc 5 antigens and about a fifth with antibodies against 1 non-arc 5 antigen. It is concluded that the EIA, standardized as described, is capable of detecting with a high degree of efficiency all the sera that should be tested by DD5 and excludes most of those in which results with DD5 have no diagnostic significance.