Serological diagnosis and post-operative surveillance of human hydatid disease. I. Latex agglutination and immunoelectrophoresis using crude cyst fluid antigen.

The latex agglutination (LA) test and immunoelectrophoresis (IEP) test for the diagnosis of hydatid disease due to Echinococcus granulosus were carried out on 3600 serum samples submitted to this laboratory during the period mid-1976 to March 1981. Of the 2280 samples submitted for primary diagnosis (no known past history of hydatid disease) there were 108 cases in which infection was confirmed, 99 of them with fertile cysts. The 'Arc 5' was demonstrated by IEP in the serum of 65.7% of cases with fertile cysts, and using the additional criterion of 3 or more arcs with no 'Arc 5', a further 13.1% of cases were diagnosed apparently without 'false positive' results. Antibody was less readily detected in the serum of patients with calcified or sterile cysts. The LA test was positive in 70.7% of patients with fertile cysts, but this test gave an unacceptably high rate of 17.6% 'false positive' results. The IEP and LA tests had a combined sensitivity of 87.9% for primary diagnosis. There were 65 confirmed cases of persistent or recurrent infection, of which 64 were positive with IEP. Forty-four of 48 cases where surgical cure was effected became IEP negative within 2 yr. Among 42 patients remaining IEP-positive beyond 2 yr after surgery, recurrent disease was confirmed in 31 cases, but it was not possible to obtain confirmation in the remaining 11 patients. The LA test was unsuitable for post-operative surveillance.