Evaluation of the gel system for ABO grouping and D typing

BACKGROUND: The gel agglutination assay has been approved by the Food and D rug Administration as an alternative to the tube assay for the detection of red cell antibodies. It has also been approved recently by the Food and Dr ug Administration for ABO blood grouping and D typing. STUDY DESIGN AND METHODS: Tube and gel agglutination assays were compared f or ABO grouping and D typing of 100 donor and 100 patient specimens. ABO gr ouping of 14 specimens of known ABO groups and D typing of 10 specimens wit h weak D were also compared. When antigen typing or isohemagglutinin result s differed, gel testing was repeated by the use of modified incubation time s, reagent or specimen volumes, and red cell concentrations. RESULTS: ABO grouping and D typing in all patient and donor specimens concu rred. B isohemagglutinins were not detected in seven group A specimens. Six of seven discrepancies were resolved when gel tests were incubated at room temperature with increased serum or plasma volume. Weak D was detected in all 10 specimens tested by both assays. When weak A and/or B were tested wi th monoclonal antibody reagents, the correct phenotypes were identified in 9 specimens by gel assay and in 10 by tube assay. Using human antisera, 6 s pecimens were correctly phenotyped by gel assay and 7 by tube assay. CONCLUSION: The gel assay performed as well as the tube assay in detection of A, B, and D, but the tube assay was slightly better at detecting B isohe magglutinins. The gel assay can be used in place of the tube assay far ABO blood grouping and D typing.