The first step for ruling out is to choose the cells appropriate for exclusion. When using the tube method, all phases should be non-reactive to rule out. If using a gel or solid phase method, only the AHG phase is examined.
Remember, an antibody will only react
with cells that have
the corresponding antigen; antibodies will not react
with cells that do not have
the antigen. This is why non-reactive cells are chosen for ruling out.
The following example is an abbreviated panel performed with a gel method. With each non-reactive cell, a rule out is performed. Below, the first non-reactive cell is examined and D, C, e, k, and s are ruled out on homozygous cells.
The second non-reactive cell is examined and c and E can be ruled out. The cell is heterozygous Ss so even though S is present on the cell, it cannot be ruled out.