Automated Reading of Red Cell Antibody Identification Tests by a Solid Phase Antiglobulin Technique

A new solid phase antiglobulin ( SPAG ) test is described which makes possible the automated reading of erythrocyte antibody identification tests. This new test uses microplates coated with anti-human globulin as a solid phase onto which previously sensitized erythrocytes adhere. A wash stage removes unsensitized erythrocytes and a chromogenic substrate is reacted with the hemoglobin peroxidase of the adhering, sensitized red cells. The color produced is read automatically on a spectrophotometer interfaced with a computer programmed to produce printouts of results. Comparative tests between conventional anti-human globulin tests and the SPAG test using titrated antibodies showed equivalent sensitivity. Comparisons of the present test system in use in our laboratory, consisting of saline, 0.5 percent bromelin, and indirect anti-human globulin techniques for identifying antibodies, with a SPAG test used in conjunction with a bromelin-enzyme test system, showed agreement in 224 (90%) of the 249 sera tested. This methodology is compared with current enzyme-linked immunosorbent assay (ELISA) techniques.