Glutaraldehyde fixed-antigen sensitized stable cells in indirect hemagglutination test for rapid diagnosis of hydatid disease, trichinosis and amoebiasis

Glutaraldehyde fixed and antigen sensitized sheep red cells (SRBC) refrigerated or lyophilized in phosphate buffered saline, pH 7·2 (PBS) or in PBS containing 3% normal rabbit serum (PBS-NRS) were stable for more than 6 months in IHA test against sera from patients with hydatid disease, trichinoisis and amoebiasis. The final concentration of protein in hydatid, trichinella and amoebic antigens used for sensitization of SRBC was 0·43, 0·75 and 1·2 mg/ml, respectively. The lyophilized cells in general showed a slightly higher sensitivity but within acceptable limits. By contrast the sensitized cells refrigerated in PBS consistently showed a uniform reactivity and IHA titres were reproducible even 6 months after sensitization of the cells. No demonstrable change was observed in the sensitivity of the test when the PBS-refrigerated cells sensitized 6 months before were exposed to room temperature for 4 days.The following are the main improvements on existing serological tests: (a) a more rapid and reproducible test for sero-epidemiological investigations in areas with minimum laboratory facilities, (b) sensitized cells could be shipped to various laboratories without losing the sensitivity of the test, (c) reduction in the cost of personnel and reagents where these tests are needed infrequently.