Given the patient's antibodies, what is the minimum number of donors that would need to be antigen typed to obtain two antigennegative donors to crossmatch?
There are two ways to calculate the minimum number of donors to antigen type:
 "Intuitive": If 7.6% of donors are Cand Jk(a) then 7.6 in 100 are negative for both antigens. If roughly 8 in 100 are negative for both, approximately 4 in 50 would be negative for both; and approximately 2 in 25 would be negative for both. To obtain two Cand Jk(a) donors, at least 25 would need to be tested.

The minimum number to antigen type can also be calculated using this formula:
# of donors (x) = # required/# antigennegative (as a decimal)
x = 2/0.076 = 26.3Depending on how lucky you feel, the minimum number to type is between 25 and 30, with 30 being on the safer side.