Evaluation and implementation of the gel test for indirect antiglobulin testing in a community hospital laboratory

Background.-The gel test, developed by Lapierre in 1984, was designed to st andardize antiglobulin testing while improving sensitivity and specificity of the method. Principle.-Anti-human serum immunoglobulin C (IgG) mixed with Sephadex G100 (gel phase) in a microtube traps red cell-IgG agglutination complexes duri ng migration through the gel in a centrifugation step. Agglutination comple xes are visibly detectable at various levels in the microtube as an inverse function of antibody coated on red cells. Unsensitized red cells form a ce ll pellet at the base of the microtube. Objective.-To determine if indirect anti-human globulin testing could be st andardized and simplified by replating the tube test with the gel test with out compromising quality or increasing costs. Setting.-A medium-sized community hospital. Results.-In a blinded retrospective study, we used pa tient sera (n = 40), which included 10 positive specimens containing 18 known antibodies. Sixtee n antibodies were detected and identified with the tube method (1 anti-D an d 1 anti-C not detected). By the gel test, 18 antibodies were detected and identified. All negative samples showed 100% concordance. Favorable results were obtained in a nonblinded prospective correlation study (n = 121). Our technologists found the gel test easier to read and more reproducible and reliable than the tube method; they also found increased sensitivity for de tecting weakly reading antibodies. We successfully introduced the gel test into our laboratory as the standard method for indirect antiglobulin testin g. Following implementation, improved personnel management was achieved. Conclusions.-The gel test is a reliable and advantageous method and is appr opriate for routine use for detection and identification of alloantibodies in a community hospital transfusion service laboratory.