RBC Antibody Screen (Red Blood Cell Antibody)

An RBC antibody screen is used to screen an individual’s blood for antibodies directed against red blood cell (RBC) antigens other than the A and B antigens. It is performed as part of a “type and screen” whenever a blood transfusion is anticipated or as part of prenatal testing of pregnant women.

The primary reason that a person may have RBC antibodies circulating in the blood is because the person has been exposed, through blood transfusion or through pregnancy, to RBCs other than his or her own (foreign RBCs). These antibodies have the potential to cause harm if a person is transfused with red blood cells that the antibodies may target or if a pregnant woman has antibodies that target the red cells of her developing baby.

If an antibody is detected, then an antibody identification test must be done to determine which antibodies are present. During a crossmatch, a variation of the RBC antibody screen is performed if clinically significant antibodies are present. In the case of blood transfusions, RBC antibodies must be taken into account and donor blood must be found that does not contain the antigen(s) to which the person has produced antibodies.

If someone has an immediate or delayed reaction to a blood transfusion, a health practitioner will order a direct antiglobulin test (DAT) to help investigate the cause of the reaction. (The DAT detects RBC antibodies attached to red blood cells.) An RBC antibody screen will be performed to see if the affected person has developed any new antibodies if the DAT is positive.

During pregnancy, the RBC antibody screen is used to screen for antibodies in the blood of the mother that might cross the placenta and attack the baby’s red cells, causing hemolytic disease of the newborn (HDN). The most serious cause is an antibody produced in response to the RBC antigen called the “D antigen” in the Rh blood group system.

A person is considered to be Rh-positive if the D antigen is present on the person’s RBCs and Rh-negative if the D antigen is not present. An Rh-negative mother may develop an antibody when she is exposed to blood cells from an Rh-positive fetus. To prevent this, an Rh-negative mother should have an RBC antibody screen performed early in her pregnancy, at 28 weeks, and again at the time of delivery. If there are no Rh antibodies present at 28 weeks, then the woman is given an injection of Rh immune globulin (RhIg) to clear any Rh-positive fetal RBCs that may be present in her bloodstream to prevent the production of Rh antibodies by the mother.

At birth, the baby’s Rh status is determined. If the baby is Rh-negative, then the mother does not require another RhIg injection; if the baby is Rh-positive and the mother’s antibody status is negative for anti-D, the mother is given additional RhIG.

This test also may be used to help diagnose autoimmune-related hemolytic anemia in conjunction with a DAT. This condition may be caused when a person produces antibodies against his or her own RBC antigens. This can happen with some autoimmune disorders, such as lupus, with diseases such as lymphoma or chronic lymphocytic leukemia, and with infections such as mycoplasma pneumonia and mononucleosis. It can also occur in some people with the use of certain medications, such as penicillin.

• An RBC antibody screen is performed prior to any anticipated blood transfusion.
• An RBC antibody screen is performed early in pregnancy as part of every woman’s pregnancy workup. In Rh-negative women, it is also done at 28 weeks, prior to giving an injection of Rh immune globulin (RhIg), and after delivery if the baby is determined to be Rh-positive. In negative pregnant women with known antibodies, the RBC antibody screen is sometimes ordered as a monitoring tool to roughly track the amount of antibody present.

Transfusion: If an RBC antibody screen is positive, then one or more RBC antibodies are present. Some of these antibodies will be more significant than others. When an RBC antibody screen is used to screen prior to a blood transfusion, a positive test indicates the need for an antibody identification test to identify the antibodies that are present. Once the antibody has been identified, donor blood must be found that does not contain the corresponding antigen(s) so that the antibody will not react with and destroy donor RBC antigens following a blood transfusion.

Pregnancy: If an Rh-negative mother has a negative RBC antibody screen, then an Rh immune globulin injection is given within 72 hours to prevent antibody production. If she has a positive test, then the antibody or antibodies present must be identified. If an antibody to the D antigen has been actively formed by the mother, then the RhIg injection is not useful. If she has a different antibody, then the RhIg injection can still be given to prevent her from producing antibodies to the D antigen.

A circulating RBC antibody, once present, will never truly go away but may drop to undetectable levels. If the person is exposed to the antigen again, production will kick quickly into gear and attack the RBCs so the antibody will be honored (treated as though it is present) even when not detectable.

Each blood transfusion that a person has exposes that person to the combination of antigens on the donor’s RBCs. Whenever the transfused RBCs contain antigens foreign to the recipient’s RBCs, there is the potential to produce an antibody. If someone has many blood transfusions over a period of time, that person may produce antibodies against many different antigens. This can make finding compatible blood increasingly difficult.

Prior to development of the injection, Rh-negative mothers would often become sensitized from the blood of their first Rh-positive baby and begin developing anti-Rh antibodies. Any subsequent Rh-positive babies would have some degree of Rh disease, due to the mother’s anti-Rh antibodies attacking the baby’s RBCs. Miscarriages and stillborn babies were relatively common, and those babies who were born often needed immediate blood transfusions to survive. The immune globulin injection has largely prevented these complications, although a small percent of women do still develop Rh antibodies.

Yes. Hemolytic disease of the newborn may occur when there is an ABO incompatibility between mother and baby, especially with mothers who are blood group O. However, the RBC antibody screen is not useful in this situation because our bodies naturally produce antibodies against the A and B antigens we do not have on our red blood cells. A mother who is blood type A will naturally have antibodies directed against the B surface antigens on red blood cells, and a mother who is type B will have anti-A antibodies, and so on. Generally, this is a mild form that is easily treatable.

No, you will not be exposed to anyone else’s blood while donating.