If a patient is hypothesized to have an anti-Fya after the initial antibody screen and panels are completed but anti-E could not be ruled out, a cell should be selected to do so. This rule-out cell should meet the following criteria:
Negative for Fya (so it will not react with the anti-Fya that has been identified in the serum of the patient).
Homozygous for big E (big E-positive and little e-negative, so that it will react most strongly with anti-E if present).
In the panel shown below, four cells (3–6) meet the first criterion (Fya negative). Of these cells, three (4-6) are big E-positive, and of these, only one cell (4) is homozygous for E (big E positive and little e negative). Therefore, cell 4 would be a suitable rule-out cell in this case.