Blood typing determines someone’s blood type through a laboratory test before a blood transfusion or organ transplant. Karl Landsteiner discovered blood types in 1901, and a person’s blood type is determined by inherited antigens. Incompatible blood can still occur even with typing due to rare antibodies.
Blood typing is a type of laboratory test that is used to determine someone’s blood type by reacting a blood sample with various reagents. This test is done before a blood transfusion to determine which type of blood can be used in the transfusion, and is also part of the battery of tests done to prepare for an organ transplant. It can also be a useful diagnostic tool for some types of medical problems.
Humans have experimented with blood transfusion for a long time, but were often unsuccessful at first. Some transfusions seemed to benefit, while others fell ill and sometimes died. It wasn’t until 1901, when Karl Landsteiner discovered blood types, that people understood why some transfusions were given while others weren’t.
A person’s blood type is determined by a set of inherited antigens. A well-known typing system is the ABO system, in which people can have A, B, AB, or O blood. The Rh blood group, which includes Rh+ and Rh- blood, is another blood group system. There are many others, all of which can be tested and can be tested among people with unique or unusual genetic inheritances.
When typing is performed, a blood sample is taken from the patient and exposed to the reagents. If a reaction occurs, it means that the blood has antibodies against a particular blood group, meaning it cannot belong to that blood group. Several techniques can be used to narrow down someone’s type through a series of reactions to various reactants.
The reactions can be observed under a microscope. Incompatible blood will pool or react in other ways suggesting that an antibody reaction is occurring on the microscope slide due to exposure to the antigens in the reagents. Some high school science classes do ABO typing as part of an introduction to blood types and genetic inheritance, using kits that allow people to check for background antibodies.
Some people are surprised to learn that even with typing, incompatibilities can still occur. This is because comprehensive testing for every known blood type is not usually done, because it is expensive and time consuming. People can be of the same blood group and still have incompatible blood within another blood group system. This allows someone to have rare antibodies that could cause an adverse transfusion reaction even after screening to rule out potential bad donors based on common antibodies.
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