What are the other Names for this Test? (Equivalent Terms)
- ABO Grouping and Rh Typing
- Blood Grouping
- Blood Grouping and Typing
What is Blood Typing Test? (Background Information)
- Red blood cells (RBCs) contain antigens on their surface
- Antigens are those substances that activate the body’s immune system to produce proteins, called antibodies
- The presence or absence of some of these antigens on an individual’s RBCs, determines his/her blood group
Two such major antigens, present on RBCs are denoted as A and B, accordingly:
- An individual with antigen A on his/her RBCs, is said to have A blood group
- An individual with antigen B on his/her RBCs, is said to have B blood group
- An individual with both, antigens A and B on his/her RBCs, is said to have AB blood group
- An individual with neither antigen A, nor antigen B on his/her RBCs, is said to have O blood group
The Rh (rhesus) factor is yet another antigenic determinant of blood group. Otherwise denoted as antigen D, an individual can be Rh+ (Rh positive) or Rh– (Rh negative), depending on the presence/absence of antigen D, on the surface of the RBCs.
The human body produces antibodies against antigens that are not normally present in the body. However, when antibodies are produced against “self” antigens (one’s own antigens), as these are perceived as “foreign” or “invaders”; then, it leads to a collection of diseases, termed as auto-immune diseases. Antibodies against A and B antigens occur naturally in blood, as follows:
- An individual with antigen A on the RBCs (blood group A), will have antibodies against B antigen (anti B)
- An individual with antigen B on the RBCs (blood group B), will have antibodies against A antigen (anti A)
- An individual with both, antigens A and B on the RBCs (blood group AB), will have no antibodies in blood
- An individual having neither antigen A nor antigen B on the RBCs (blood group O), will have antibodies against both A and B (both anti A and anti B) in blood
Antibodies against the D antigen (Rh factor) are not naturally present in blood. However when an Rh negative individual, receives blood from an Rh positive individual, he/she begins producing antibodies against the D antigen, as this is perceived “foreign”.
The reaction between antigens and the corresponding antibodies, causes the agglutination/clumping (grouping) of RBCs, leading to their eventual destruction. This property is made use of in the laboratory, to determine an individual’s blood group.
What are the Clinical Indications for performing the Blood Typing Test?
Indications for performing Blood Typing include:
- To determine the blood group (or blood type) of an individual, who needs to receive blood, which could be following the loss of blood, which could be due to trauma, surgery, bleeding disorder, or suffering from diseases with increased RBC destruction, or having severe anemia
- To determine the blood group of an individual donating blood
- To rule out blood group, mainly Rh incompatibility, between mother and child during pregnancy
When an Rh negative mother carries an Rh positive baby, she gets exposed to some of the RBCs crossing over from the baby at the time of birth and begins producing antibodies against the D antigen. Although, the first child remains unharmed; however, during any subsequent pregnancy with an Rh positive fetus, the maternal antibodies cross-over into the fetal circulation, leading to destruction of the baby’s RBCs. This leads to a condition called erythroblastosis fetalis (or hemolytic disease of the newborn), which may prove fatal in severe cases.
How is the Specimen Collected for Blood Typing Test?
Sample required: Blood
- In Adults: Blood sample is drawn via a finger prick, or through a needle inserted into a vein (on the arm)
- In newborns: Blood sample is drawn from the umbilical cord, immediately on birth, or from the heel after making a small nick using a scalpel (heel stick)
Preparation required: None
What is the Significance of the Blood Typing Test Result?
- Blood Typing helps in identifying the compatibility between a donor and a recipient, in case of a blood transfusion
- Whenever an individual receives incompatible blood during transfusion, it leads to transfusion reactions that may produce symptoms, such as fever, chills, nausea, headaches, which may further lead on to kidney failure, or may even prove fatal
To avoid such reactions, the permissible recipient - donor pairs are:
- A positive recipient - can receive A positive, A negative, O positive, O negative donor blood
- A negative recipient - can receive A negative, O negative donor blood
- B positive recipient - can receive B positive, B negative, O positive, O negative donor blood
- B negative recipient - can receive B negative, O negative donor blood
- AB positive recipient - can receive AB positive, AB negative, A positive, A negative, B positive, B negative, O positive, O negative donor blood
- AB negative recipient - can receive AB negative, A negative, B negative, O negative donor blood
- O positive recipient - can receive O positive, O negative donor blood
- O negative recipient - can receive O negative donor blood
Determination of the Rh status of a pregnant woman and that of the newborn helps in planning the use of anti D immunoglobulin, in order to prevent hemolytic disease of the newborn.
- Rh negative women with Rh positive partners should receive anti D immunoglobulin (Rh Ig prophylaxis)
- Rh negative woman, who has just delivered an Rh positive baby, should receive anti D immunoglobulin again
The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.
Additional and Relevant Useful Information:
In addition to A, B and D antigens, other antigens, called minor blood group antigens, are present on the surface of the red blood cells. These include Kidd, Kell, Duffy, and other Rh system antigens. Antibodies to these antigens do not occur naturally.
Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.