The patient's pretransfusion red cells and all donor red cells involved in the case (group O Rh-negative Red Blood Cell units transfused and four group O Rh-positive red cells initially crossmatched) were phenotyped for Jka. As expected, the patient typed as Jk(a-). The six donor RBCs incompatible in the initial crossmatch were Jk(a+).
The frequency of the Jka gene in Caucasians is ~77%, with most Caucasian red cells (50%) typing as Jk(a+b+).
