Compatibility test in the blood transfusion

A compatibility test in the blood transfusion, also known as crossmatching, is a laboratory procedure performed before a blood transfusion to ensure that the donor’s blood is compatible with the recipient’s blood. The test aims to prevent hemolytic reactions when the recipient’s immune system attacks incompatible donor red blood cells (RBCs). This test includes ABO compatibility, Rh compatibility, and a more specific crossmatch test to detect other antibodies that may cause transfusion reactions.

Types of Compatibility Tests for Blood Transfusion:

1. ABO Compatibility Test
2. Rh Compatibility Test
3. Crossmatching Test
4. ABO Compatibility Test

1. ABO Compatibility Test

• The first step in blood transfusion is ensuring the ABO blood type of the donor and the recipient are compatible.
• ABO incompatibility can lead to serious or fatal hemolytic reactions because the recipient’s immune system will produce antibodies against the donor blood’s A or B antigens if they are incompatible.

 

Donor Blood Type	Recipient Blood Type	Compatibility
O	O, A, B, AB	Universal donor for all blood types (no A or B antigens)
A	A, AB	Can donate to A or AB
B	B,AB	Can donate to B or AB
AB	AB	Can only donate to AB (but universal recipient)

 

• O- is the universal donor in emergencies because it lacks both A/B antigens and the Rh factor.
• AB+ is the universal recipient, as they have no anti-A, anti-B, or anti-Rh antibodies.

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2. Rh Compatibility Test

• The Rhesus (Rh) factor must also match between donor and recipient. Rh incompatibility occurs if a Rh-negative recipient receives Rh-positive blood, potentially causing the recipient to form antibodies against Rh-positive red cells.
• Rh-negative individuals can only safely receive Rh-negative blood.

Rh Compatibility Table:

Donor Rh Type	Recipient Rh Type	Compatibility
Rh+	Rh+	Compatible
Rh-	Rh+ or Rh-	Compatible
Rh+	Rh-	Incompatible

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3. Crossmatching Test

Crossmatching is a more specific test conducted after confirming ABO and Rh compatibility to ensure there are no other antibodies in the recipient’s blood that might attack the donor’s red blood cells. There are two types of crossmatching:

• Major Crossmatch:
  • Procedure: The recipient’s plasma (which may contain antibodies) is mixed with the donor’s red blood cells.
  • Purpose: To detect antibodies in the recipient’s blood that might attack the donor’s RBCs, causing agglutination or hemolysis.
  • Result: The crossmatch is compatible if no agglutination (clumping) occurs.
• Minor Crossmatch:
  • Procedure: The donor’s plasma is mixed with the recipient’s red blood cells.
  • Purpose: To detect antibodies in the donor’s blood that might react with the recipient’s RBCs.
  • Result: It is less frequently performed as donated blood is generally screened and processed to remove plasma (and thus antibodies).

Crossmatch Test Procedure:

1. Blood Collection: Blood samples from the donor and the recipient are collected.
2. Mixing:
   • Major Crossmatch: The recipient’s plasma is mixed with the donor’s red cells.
   • Minor Crossmatch: The donor’s plasma is mixed with the recipient’s red cells.
3. Observation: The mixtures are observed for agglutination, indicating incompatibility.
4. Interpretation:
   • Compatible Crossmatch: No agglutination is observed; the blood transfusion can proceed.
   • Incompatible Crossmatch: Agglutination occurs, indicating that the blood types are incompatible, and a different donor must be found.

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Compatibility Test Process:

1. ABO and Rh Testing: Ensures compatibility based on the basic blood group and Rh factor.
2. Antibody Screening: The recipient’s blood is screened for unexpected antibodies against other blood group antigens (such as Kell, Duffy, Kidd, etc.).
3. Crossmatching: The major crossmatch is performed to check for any possible reactions between the recipient’s antibodies and the donor’s red blood cells.

Importance of Compatibility Testing:

• Prevents Transfusion Reactions: The main goal is to avoid severe transfusion reactions, such as acute hemolytic reactions, which occur when incompatible red cells are destroyed by the recipient’s immune system. Symptoms can include fever, chills, chest pain, back pain, low blood pressure, and even kidney failure or death.
• Ensures Patient Safety: Proper compatibility testing reduces the risk of delayed hemolytic reactions, where antibodies not detected during initial screening cause red cell destruction days or weeks after the transfusion.