Final answer:
The Kleihauer-Betke test is used to detect the presence and amount of fetal blood in the maternal circulation when there's a risk of Rh isoimmunization. The indirect Coombs' test screens for unbound antibodies in a patient's serum, and the direct Coombs' test can be used to determine if maternal antibodies have bound to the newborn's red blood cells.
Step-by-step explanation:
The test that detects the presence and amount of fetal blood in the maternal circulation when there's a risk of Rh isoimmunization is the Kleihauer-Betke test. This test is particularly relevant for Rh- mothers who have an Rh+ fetus, as fetal erythrocytes can enter the mother's bloodstream and trigger the production of anti-Rh antibodies. These antibodies can cross the placenta during a subsequent pregnancy and cause hemolysis of fetal erythrocytes, leading to conditions like Erythroblastosis Fetalis. In contrast, the indirect Coombs' test (IAT) and the direct version are used to screen for antibodies against red blood cell antigens. While the indirect Coombs' test screens for unbound antibodies in a patient's serum, the direct Coombs' test is employed when a newborn presents with jaundice to determine if the mother's antibodies have bound to the child's red blood cells. Another test, the antibody screening test, ensures that blood transfusion recipients do not have antibodies against donor red blood cell antigens.