Level of HLA-A and HLA-B genotypic mismatching identified following DNA typing for the URD in the 6/6, 5/6, and 4/6 original match subgroups. In comparison to the original 6/6 group, degree of genotypic mismatching was significantly higher for the 5/6 (P< .005) and the 4/6 (P < .001) group. There was no statistical difference between 4/6 and 5/6 original subgroups. The number of URD in each category is shown next to the column with percentage values in the parenthesis.