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ABO GROUPING AND Rh D GROUPING

Published in Hemotology
Friday, 21 July 2017 06:48
ABO Grouping

There are two methods for ABO grouping:
 
  • Cell grouping (forward grouping): Red cells are tested for the presence of A and B antigens employing known specific anti-A and anti-B (and sometimes anti-A, B) sera.
  • Serum grouping (reverse grouping): Serum is tested for the presence of anti-A and anti-B antibodies by employing known group A and group B reagent red cells.

Both cell and serum grouping should be done since each test acts as a check on the other.
 
There are three methods for blood grouping: slide, tube and microplate. Tube and microplate methods are better and are employed in blood banks.
 
Further Reading:
 

FALSE REACTION IN ABO GROUPING

Published in Hemotology
Friday, 21 July 2017 06:19
  1. Autoagglutination: Presence of IgM autoantibodies reactive at room temperature in patient’s serum can lead to autoagglutination. If autocontrol is not used, blood group in such a case will be wrongly typed as AB. Therefore, for correct result, if autocontrol is also showing agglutination, cell grouping should be repeated after washing red cells with warm saline, and serum grouping should be repeated at 37°C.
  2. Rouleaux formation: Rouleux formation refers to red cells adhering to each other like a stack of coins and can be mistaken for agglutination. Rouleaux formation is caused by high levels of fibrinogen, immunoglobulins, or intravenous administration of a plasma expander such as dextran. Rouleaux formation (but not agglutination) can be dispersed by addition of normal saline during serum grouping.
  3. False-negative result due to inactivated antisera: For preservation of potency of antisera, they should be kept stored at 4°-6°C. If kept at room temperature for long, antisera are inactivated and will give false-negative result.
  4. Age: Infants start producing ABO antibodies by 3-6 months of age and serum grouping done before this age will yield false-negative result. Elderly individuals also have low antibody levels.

Rh D GROUPING METHOD

Published in Hemotology
Friday, 21 July 2017 05:47
D antigen is the most immunogenic after ABO antigens and therefore red cells are routinely tested for D. Individuals are called as Rh-positive or Rh-negative depending on presence or absence of D antigen on their red cells. Following transfusion of Rhpositive blood to Rh-negative persons, 70% of them will develop anti Rh-D antibodies. This is of particular importance in women of childbearing age as anti-D antibodies can crosss the placenta during pregnancy and destroy Dpositive fetal red cells and cause hemolytic disease of newborn. In other sensitized individuals, reexposure to D antigen can cause hemolytic transfusion reaction.
 
In Rh D grouping, patient’s red cells are mixed with anti-D reagent. Serum or reverse grouping is not carried out because most Rhnegative persons do not have anti-D antibodies; anti-D develops in Rh-negative individuals only following exposure to Rh-positive red cells.
 
Rh typing is done at the same time as ABO grouping. Method of Rh D grouping is similar in principle to ABO grouping. Since serum or reverse grouping is not possible, each sample is tested in duplicate. Dosage effect (stronger antigenantibody reaction in homozygous cells i.e. stronger reaction with DD) is observed with antigens of the Rh system. Autocontrol (patient’s red cell + patient’s serum) and positive and negative controls are included in every test run. Monoclonal IgM anti-D antiserum should be used for cell grouping, which allows Rh grouping to be caried out at the same time as ABO grouping at room temperature. With monoclonal antisera, most weak and variant forms of D antigen are detected and further testing for weak forms of D antigen (Du) is not required. Differences between ABO and Rh grouping are shown in Table 788.1.
 
Table 788.1 Comparison of ABO grouping and Rh typing
Comparison of ABO grouping and Rh typing

Microplate Technique for Rh D Grouping

Published in Hemotology
Friday, 21 July 2017 05:28
Microplate is a polystyrene plate consisting of 96 micro wells of either U- or V-shape. Grouping is carried out in micro wells. This method is sensitive and ideal for large number of samples (see Figure 787.1).
 
Further reading: Rh D GROUPING METHOD

Blood Banking and Transfusion Medicine

Published in Downloads
Sunday, 28 May 2017 14:35

Description: Ever since the discovery of blood types early in the last century, transfusion medicine has evolved at a breakneck pace. This second edition of Blood Banking and Transfusion Medicine is exactly what you need to keep up. It combines scientific foundations with today's most practical approaches to the specialty. From blood collection and storage to testing and transfusing blood components, and finally cellular engineering, you'll find coverage here that's second to none. New advances in molecular genetics and the scientific mechanisms underlying the field are also covered, with an emphasis on the clinical implications for treatment. Whether you're new to the field or an old pro, this book belongs in your reference library.

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