Rh Case Study, ID Panel crossout

In the antibody identification panel below, the crossout technique was employed to show how various specificities were ruled out. Cells that have negative reactions in all phases of testing are used to eliminate the specificities against which the antibody is directed. In this example, the first cell with a negative reaction through all phases is number 3. A line is placed through the antigen specificity that is positive for that cell on the panel. Using this method, cell 3 assists in eliminating D, c, E, k, Fy^b, Jk^b, Le^b, P1, N and s specificities. Continuing in this manner, cell 4 eliminates Jk^a, e, and S specificities. Cells 6 eliminates Le^a and M specificities. Cell 7 eliminates K and cell 8 eliminates Fy^a. It is best to crossout using cells that express a double dose (homozygosity) of a given antigen since some antibodies show dosage effect and may not react with those cells. One exception is the K antigen given that homozygosity for K is extremely rare.

Next, observe the pattern of reactivity. In this case the pattern of reactivity is highlighted in yellow and matches that of C. Finally, the "rule of three" test must be considered to ensure that the reactions have a high probability of being the result of anti-C rather than being a random event. (p value of 0.05) The rule of three states that at least three antigen positive cells must react and at least three antigen negative cells do not react. In this case there are four antigen positive cells that react and seven antigen negative cells that do not react, therefore we have met the rule of threes.