Playing with Enzymes

A 70-year-old female of African American decent, with history of hypertension, type II diabetes mellitus, anemia, and congestive heart failure, is admitted because of symptomatic anemia (hemoglobin, Hgb level 7.2 g/dL). The patient has a history of red blood cell (RBC) transfusions and is known to have alloantibodies (anti-C, -K, and -Fya). The patient was last transfused two units of RBCs 2 weeks ago. Two RBC units are now requested, and a type and crossmatch sample (ethylenediaminetetraacetic acid, EDTA anticoagulant) is submitted to the blood bank.