A new serum hydatid antigen detection test for diagnosis of cystic echinococcosis.

Cystic echinococcosis (CE) is a major public health problem with a worldwide distribution in both humans and animals. Diagnosis of this disease by simple and rapid immunoassays is a priority. The objective of the present study was to standardize and evaluate the latex agglutination test (LAT) as a simple test for the detection of circulating hydatid antigen in serum. The subjects in this study included 141 patients in the following groups: surgically confirmed CE cases (18), ultrasound-proven cases (26), presumptive CE cases (47), controls with other parasitic disease (25), and healthy controls (25). A polystyrene latex (0.81 microm) suspension was used as a carrier particle for hydatid antibodies in the test. The latex particles were sensitized with hyperimmune hydatid antiserum raised in rabbits. The hydatid antibody-sensitized latex particles were used for the detection of hydatid antigens in serum. The results of the study showed that the LAT could detect the circulating hydatid antigen in 13 (72%) of 18 patients with surgically confirmed CE, 17 (65%) of 26 patients with ultrasound-proven CE, and 19 (40%) of 47 presumptive cases of CE. The test detected antigen in 1 (4%) of 25 controls with other parasitic disease, and no antigen was detected in the serum of 25 healthy controls. The LAT showed a sensitivity of 72%, a specificity of 98%, a positive predictive value of 93%, and a negative predictive value of 91%. The present study is the first report of the LAT for the detection of hydatid antigen in serum in the diagnosis of CE.