A previously transfused patient has a negative antibody screen, but one of three donor units is incompatible at the antiglobulin phase. What is the most likely cause?
1An antibody to a low-incidence antigen present on that donor unit✓ 정답
2A cold reacting autoantibody that is active at the antiglobulin phase
3An ABO typing error involving the patient sample or that unit
4Rouleaux formation caused by an increased serum protein level
해설
Screening cell panels usually lack low-incidence antigens, so an antibody to a low-incidence antigen is missed on screening and shows up only against the one donor unit that carries that antigen. A cold autoantibody or an ABO error would make several units incompatible, not just one.