Antigen phenotyping cannot normally be done on a patient who has been recently transfused. What is usual time limit?

Antigen typing should not be done on a patient who has been transfused within the past 3 months. Mrs. AL was transfused on April 2 and it is now June 22, a period of 12 weeks.

Accordingly, the decision was made to type the patient and evaluate results carefully, looking particularly for mixed field agglutination in typing results (which would indicate two cell populations). In this case the patient typed negative for the antigens of interest (E, K, Jka), corresponding to the unexcluded antibodies.