Blood Group Test (ABO Rh Typing)

Blood group testing is important for:

• Blood donations
• Blood transfusions
• Organ donation

Receiving blood from a wrong blood group, may trigger a severe immune response as the antibodies react against the foreign particles which can at times even be fatal.

Abo rh test measures the presence of antigen (A, B antigen) and Rh factor in the blood. Based on this, the blood group type is determined. 

The blood sample is taken from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a  little sting when the needle goes in or out. This usually takes less than five minutes.

Type A: Those with blood group A have presence of antigen A and antibody against B. Thus, they can receive blood from people with blood group A and blood group O. But, can donate blood only to those with blood group A. Type B: Those with blood group B have presence of antigen B and antibody against A. Thus, they can receive blood from people with blood group B and blood group O. But, can donate blood only to those with blood group B. Type AB: Those with blood group AB have presence of antigen A and antigen B. Thus, they can receive blood from people with blood group A, blood group B, blood group AB and blood group O. They are known as universal receivers. But, can donate blood only to those with blood group AB. Type O: Those with blood group O have no antigen. Thus, they can donate blood to all blood groups. They are known as universal donors. But, they have presence of antibodies against A and B. Hence, can receive blood only from type O blood group. Rh+ : Rh factor protein is present on the surface, hence they can receive blood from those with Rh+ and Rh-. Rh- : Rh factor protein is absent on the surface, hence they can receive blood only from those with Rh-.

If the mother is Rh negative and conceives a child who is Rh positive, it could lead to RH incompatibility in which the mother's blood when in contact with the fetal blood can develop antibodies against the fetal RBCs. These antibodies can cross the placenta and destroy the fetal RBCs which can lead to a hemolytic disease in which the fetus has extremely low levels of RBCs.

When an individual's RBC lacks the basic H antigen, they have a blood type known as a Bombay blood group. These people also lack A and B antigens, as the development of these antigens requires the presence of the H antigen. Persons with the Bombay blood group can only receive blood from people with the same blood group since their bodies can acquire antibodies to antigens A, B, and H.

A person with O negative blood group does not have any antigen on their RBCs and so infusing their blood in someone's body will not lead to the formation of any antibodies therefore they can safely donate blood to people with any blood group.

You cannot be a blood donor if you have sexually transmitted diseases like HIV positive, have or are carriers for diseases like Hepatitis B or C carrier, or have taken injections with drugs.

Blood typing involves two steps:

1. Forward typing: Your healthcare provider obtains a small amount of blood sample from you which is tested against two solutions- one having antibodies against the A antigen (Anti-A) and one with antibodies against the B antigen (Anti-B)

If your RBCs have the A antigen when the blood sample is added to the anti-A solution, the blood cells will clump together and this process is called agglutination. This will mean that you have an A type of blood group. If this happens only for anti-B, then your blood group is B. If your blood reacts for both Anti-A and Anti-B solution, then you have AB blood group and if there is no reaction for both, it is O-type blood.

1. Reverse typing: In this second step, the plasma of the blood is mixed with type A and type B blood separately to check the reaction. The occurrence or the absence of agglutination confirms the results of forward typing.

This test is used to determine the Rhesus blood type. In this test, the blood sample is mixed with a solution having antibodies for the Rhesus factor. The blood reacting to the Rh antibodies with agglutination hints at the fact that the blood is Rh-positive and if there is no reaction then it is an Rh-Negative blood type

• Blood Grouping Test
• ABO Blood Typing
• Rhesus Typing