Comparison of three immunological tests for seroepidemiological purposes in human echinococcosis

The comparative sensitivity and specificity of three immunodiagnostic tests for hydatid disease--the latex agglutination (LA) test, the indirect haemagglutination (IHA) test and the counterimmunoelectrophoresis (CIEP) test--were studied. The results of the IHA test were evaluated using three positivity criteria. Antigen from the same source--hydatid cyst fluid pool of ovine origin--was utilized for the three tests. A total of 123 sera were studied; 30 preoperative sera from patients with other parasitic and infectious diseases, 30 sera from patients with non-parasitic diseases and 30 sera from normal blood donors. The results of the three tests were correlated to the immunoelectrophoresis (IEP) test based on the presence of arc 5. The same sensitivity (86.7%) and specificity (99%) was obtained in LA, CIEP and IHA tests when the minimum cross-reactivity titre criterion was employed for the latter. Non-specificity was relatively high (13%) in the IHA test when only serological reactivity was considered. The sensitivity of the IHA test decreased (83.3%) using the diagnostic titre criterion and non-specific reactions were eliminated. All three tests correlated well with the IEP test.