Final answer:
To evaluate the effectiveness of PRBC transfusion, hematocrit levels are measured to determine the increase in RBC count following the transfusion.
Step-by-step explanation:
To evaluate the effectiveness of a Packed Red Blood Cells (PRBC) transfusion, you would measure hematocrit levels. The hematocrit test measures the percentage of Red Blood Cells (RBCs), also known as erythrocytes, in a blood sample. This test involves spinning a blood sample in a centrifuge to separate the components by weight, resulting in the erythrocytes settling at the bottom. By comparing the hematocrit levels before and after the transfusion, you can determine whether the PRBC transfusion has adequately increased the patient's RBC count, signifying an effective transfusion.