An 82-year-old patient shows 4+ agglutination with anti-A and no reaction with anti-B on forward typing. Reverse typing shows no reaction with A1 cells and no reaction with B cells. What is the most likely explanation?
1The patient is group O with a cold autoantibody
2The patient is group AB with rouleaux formation
3The patient is group A with weak or absent expected antibody✓ 정답
4The patient has an acquired B antigen
해설
Forward typing indicates group A, but the expected anti-B is missing in the reverse typing. This is a weak or absent expected antibody, seen in elderly, newborn, and immunocompromised patients. A group O patient would show no reaction in forward typing, and rouleaux causes extra reactivity in reverse typing rather than missing reactivity.