Reasons & Procedure To Conduct a Indirect Antiglobulin Test

Submitted on March 27, 2012

Indirect Antiglobulin Test

An Indirect Antiglobulin Test is particularly used to screen the blood for antibodies that are directed against the antigens present in the red blood cells. This is a mandatory test performed right before a blood transfusion takes place. If antibodies are detected, a test is conducted in order to determine the exact kind of antibodies present.


In this test, a sample of blood is taken and mixed with that of the donor. This mixing is done in a test tube, after which the test tube is left on a stand for some time. If there is any kind of clumping observed in the test tube, the transfusion is not continued. Such clumping is an indication that the two blood types are not compatible.

Sometimes the blood may not have an immediate reaction to the transfusion. In such a case your doctor may also order a direct antiglobulin test which aims to investigate the cause of a reaction between the two blood types which results in the clumping.

Reason Why It is Conducted

Indirect antiglobulin testing may also be conducted in pregnant women to check for antibodies in the mother's blood. If the antibodies in the mother's blood are not screened properly, they may attack the red blood cells in the placenta and develop complications in the pregnancy.

Though there are several causes of clumping of blood, the most serious one is the presence of D antigen which is present in the Rh blood. These antibodies are created if the mother's Rh is negative and the baby's Rh is positive. Usually, a mother who has Rh negative should ideally get a blood test done early in the pregnancy. Another test is conducted when the pregnancy is approximately 28 weeks.

A final test is then performed at the time of delivery. If in the test conducted in the 28th week indicates the presence of Rh antibodies, the pregnant woman may be given an injection to clear any Rh positive RBCs of the fetus. Some of the early signs and symptoms of blood transfusion reactions include chills, fever, presence of blood in the urine, rashes, dizziness, and pain in the back.

A positive indirect antiglobulin test means that there are one or more RBC antibodies present in the blood. Some of the antibodies are more significant than the others, and therefore need to be identified promptly. It is important to note that once the presence of an RBC antibody is detected, it may never truly go away.