Detection of antibodies in acid eluates with the gel microcolumn assay

BACKGROUND: Gel microcolumns can be used to detect unexpected serum antibodies and to determine ABO blood group and Rh phenotype. DATs can also be performed with this system. The purpose of this study was to compare the gel microcolumn to the tub IAT using anti-IgG for the detection of antibodies eluted from RBCs. STUDY DESIGN AND METHODS: Acid eluates were prepared from 30 peripheral blood and 41 umbilical cord blood samples. Twelve of the 71 eluates made were from control samples (known DAT negative). Specificities of eluted antibodies were determined by both tube and gel assays with a three-cell screen plus A, and B cells, as determined by blood type. RESULTS: Ten of 30 peripheral blood eluates were reactive in both assays. Eighteen were nonreactive in both assays, and two from patients with autoimmune hemolytic anemia were reactive by gel assays and nonreactive by tube assays. Thirty three of the 41 cord blood eluates were reactive in both assays. Eluates from 2 of the 35 DAT-positive samples reacted with A, and B cells by the tube method but were nonreactive by the gel method. Of the 33 cord blood eluates that were reactive by both assays, antibody specificity differed for two samples. When tested by tube assay, these eluates reacted with both A, and B cells, whereas the same eluates tested by gel assay showed one reacting with only A, cells and the other with only B cells. CONCLUSIONS: Results of testing eluates in gel assays were similar to those obtained in tube assays. The gel assays may be better at detecting antibodies eluted from RBCs from patients with autoimmune hemolytic anemia, and tube assays may be better at detecting isohemagglutinins eluted from umbilical cord blood.