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.
| Rh-Hr | Kell | Duffy | Kidd | Lewis | MNSs | P | Lutheran | Xg |
Donor Cell Number | D | C | c | E | e | Cw | K | k | Kpa | Jsa | Fya | Fyb | Jka | Jkb | Lea | Leb | M | N | S | s | P1 | Lua | Lub | Xga |
1 | 0 | + | + | 0 | + | 0 | 0 | + | 0 | 0 | + | + | + | + | 0 | + | + | 0 | 0 | + | + | 0 | + | 0 |
2 | + | + | 0 | 0 | + | + | 0 | + | 0 | 0 | + | 0 | + | + | + | 0 | 0 | + | 0 | + | + | 0 | + | + |
3 | + | + | 0 | 0 | + | 0 | + | + | 0 | 0 | 0 | + | 0 | + | 0 | + | + | + | 0 | + | + | 0 | + | + |
4 | + | 0 | + | + | 0 | 0 | 0 | + | 0 | 0 | 0 | 0 | + | 0 | 0 | 0 | + | 0 | 0 | + | + | 0 | + | + |
5 | 0 | 0 | + | + | + | 0 | 0 | + | 0 | 0 | 0 | + | 0 | + | 0 | + | + | + | + | + | + | 0 | + | 0 |
6 | 0 | 0 | + | + | + | 0 | 0 | + | 0 | + | 0 | 0 | + | 0 | + | 0 | + | + | 0 | + | + | 0 | + | 0 |