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Why is blood grouping important?

11 November 2019

With 9 clinically significant blood group system types found in humans, giving the correct blood to a patient during a transfusion is vitally important. This means making sure that the donor’s blood is compatible with the patient’s blood, to minimise reactions during a transfusion and avoid any catastrophic consequences. Lorne Labs are a leading manufacturer of blood transfusion supplies, and experts in blood grouping and transfusion so this guide offers everything you need to know about blood type detection.

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Blood Grouping History

Since 1900, we have known about one of the most important blood groups, the ABO blood system, discovered by Physician Karl Landsteiner. He later discovered the Rh blood group system in 1930, and with it the RhD antigen. The blood groups are defined by the presence or absence of a specific antigen on the surface of a red blood cell.

The 4 Blood Groups

Along with red blood cells, white blood cells and platelets, blood also contains antigens, part of the body's immune system. Antigens are proteins or sugars which cover the surface of the red blood cells. Some of these antigens define which blood group you belong to.

There are four ABO blood groups: A, B, AB and O which all refer to the presence of different antigens on the red blood cells. Blood group A means you have the A antigen, while blood group B means you have the B antigen. Blood group AB has both the A and B antigens present on the surface, but blood group O has neither antigen present.

People that have the D antigen on their red blood cells are RhD positive, while those people that don’t have the D antigen are Rh D negative. The positive and negative suffix on blood types, such as A+ and B- refers to your Rh D type, also known as your Rhesus D type.

The importance of blood grouping in transfusions

The accurate grouping of blood is very important when it comes to having a blood transfusion. If blood is given to a patient that has a blood type that is incompatible with the blood type of the blood that the patient receives, it can cause intravenous clumping in the patient’s blood which can be fatal. The patient’s body can start producing antibodies that attack the antigens on the blood cells in the blood that was given to the patient, causing reaction and rejection.

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For example, a patient who is blood group B has naturally occurring Anti-A antibodies in their blood plasma. If this (blood group B) patient receives blood group A red cells, the Anti-A antibodies in the plasma of the patient will cause the blood group A red cells to clump intravenously (within the veins), which is life threatening.

Similarly, a patient who is blood group A has naturally occurring Anti-B antibodies in their blood plasma. If this (blood group A) patient receives blood group B red cells, the Anti-B antibodies in the plasma of the patient will again cause the blood group B red cells to clump intravenously which poses the same life threatening risks.

Packed blood group O red cells (that do not contain significant amounts of plasma and therefore no significant amounts of naturally occurring antibodies) can be given safely to any other blood group. Considering that a person can be either blood group A, B, AB or O and is either blood group RhD positive (also denoted as +) or RhD negative (also denoted as -), this means that a person can be one of eight ABO and RhD blood groups: A+ (A RhD positive), A- (A RhD negative), B+, B-, AB+, AB-, O+, O-. The compatibility between these groups is detailed in a table in the next section.

The rarest blood groups amongst the population that donate blood in the UK are AB-, whereas the most common are O+. People who are blood group RhD positive, can be given either RhD positive or RhD negative blood, but people with RhD negative blood can only receive RhD negative blood. With so many possible scenarios, identifying a patient’s blood group quickly and accurately and identifying the best blood or platelets to provide for the transfusion process is serious.

To complicate matters further, it’s also possible for your blood type to change in some circumstances. As most red blood cells are made in the body’s bone marrow, transplanted bone marrow from a donor of a different type will cause your blood type to change over time. During this transition period, monitoring blood types is again important in case of other transfusions being required.

Safe blood groups in blood and plasma transfusion

This table details which red cells and plasma can be received from which donor types. Plasma is the largest component of blood and is the clear, yellow liquid that holds the red blood cells, white blood cells, platelets and other cellular components in suspension. As plasma contains water, salts, enzymes, antibodies and other proteins, and the blood type is dictated by many of these contents, plasma also carries a type.

Patient Blood Group Compatible Donor Red Cells Compatible Donor Plasma
O- O- O-,O+,AB-,AB+,A-,A+B+,B-
O+ O-,O+ O-, O+, AB-, AB+
A- O-,A- O-,O+,AB-,AB+
A+ O-,O+,A-,A+ O-,O+,AB-,AB+
B- O-,B- B-,B+,AB-,AB+
B+ O-,O+,B-,B+ B-,B+,AB-,AB+
AB- O-,A-,B-,AB- AB-,AB+
AB+ O-,O+,A-,A+,B-B+,AB-,AB+ AB-,AB+

The importance of blood grouping during pregnancy

Blood typing is particularly important for pregnant women, as blood groups are hereditary and can be passed from either the mother or father. In cases where the father of the baby has the RhD positive blood group and the mother of the baby has the RhD negative blood group, the baby may be RhD positive which can cause compatibility issues. If the baby has the RhD positive blood group, it may cause medical complications. In this case a special drug is administered to the mother to stop the mother’s body producing antibodies against the baby’s blood cells.

How blood grouping reagents work

Blood group reagents are solutions that are used to determine blood groups. The reagents contain antibodies that will detect the presence of the appropriate antigens on the surface of red blood cells.

The reagents can cause the agglutination (clumping) on the test red blood cells which carry the appropriate antigen. No clumping of the test red blood cells indicates the absence of the appropriate antigen.

There are several techniques that can be used to detect blood groups. All techniques are based on the binding of an antibody to the appropriate antigen which is called agglutination. The agglutination can be seen macroscopically as the clumping together of the red cells.

The Direct Antiglobulin Technique (DAT) involves washing the test cells in a saline solution in a test tube. After the washing of the red cells, the saline solution is removed from the test tube and a bridging reagent (Anti-Human Globulin reagent) is added to the red cells in the test tube. The test tube is spun in a centrifuge. The test result (agglutination or no agglutination) is read macroscopically.

The Indirect Antiglobulin Technique (NISS IAT) requires the red cells to be mixed in a test tube with a blood grouping reagent. The test tube (containing the blood grouping reagent and the red cells) is incubated at 37 °C for 15 minutes. After incubation, the red cells are washed with a saline solution. After washing the red cells, the saline solution is removed from the test tube and a bridging reagent (Anti-Human Globulin reagent) is added to the red cells in the test tube. The test tube is spun in a centrifuge. The test result (agglutination or no agglutination) is read macroscopically.

Getting Started with Blood Grouping

Lorne Labs offer a range of Blood Transfusion Supplies including Blood Grouping Reagents, Blood Transfusion Equipment, Red Cells, Enzymes and Potentiators and Quality Control Kits. Lorne is also the UK's distributor of Millipore Blood Grouping Reagents.

With high customer service standards and quality lab equipment. Lorne laboratories is able to offer health care professionals affordable laboratory tools and a leading service within the medical industry.

If you are a blood transfusion professional from the UK and would like to learn more about our range of Blood Transfusion Supplies or place an order for Lorne Labs' Blood Grouping Reagents,  e-mail us at or call +44 (0) 118 921 2264. If you're outside the UK, find your nearest distributor by visiting our distributors page

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