Evaluation of an enzyme-linked antiglobulin test for the detection of red cell antibodies

An enzyme-linked antiglobulin test (ELAT) using low ionic strength saline for the initial red cell sensitisation phase, and alkaline phosphatase conjugated antiglobulin (AP-AHG), has been compared with a conventional low ionic strength antiglobulin test in testing 222 red cell antibodies of various specificities. A wide variation in absorbance values was observed at all levels of haemagglutination strength. Relatively higher absorbance values were obtained with anti-K compared with the agglutination gradings. Haemolysis was eliminated by modifying the substrate buffer used for diluting the AP-AHG, since fixation of red cells prior to sensitisation significantly reduced the sensitivity of the ELAT. Five commercial AP-AHG reagents compared to tests with D, Fya, K and Jka antibodies varied markedly in performance, some being unsatisfactory. The ELAT can be effectively used for antibody detection as well as quantitative determinations but requires automation to realise its full potential.