Test for blood transfusion: Cross Matching, Coombs Test, Blood Transfusion Reactions

Cross matching

Blood transfusion reaction may occur between the donor’s blood and the recipient’s blood during blood transfusion. Blood transfusion reaction occurs due to incompatibility between the donor’s blood and the recipient’s blood. This can be prevented by cross-matching.

There are two primary steps in cross-matching. These are ABO/Rh typing and compatibility testing.

1. ABO/Rh typing: ABO blood group system classifies blood into four types. These are blood group A, blood group B, blood group AB, and blood group O. This classification is based upon antigen present or absence on the red blood cells surface.

Rh system determines the presence and absence of Rh factor (Antigen-D) on the red blood cells surface.

The recipient’s blood and donor’s blood group are determined through blood typing. Compatibility of the ABO blood group and Rh blood group is a must in blood transfusion. Incompatible blood transfusing leads to serious complications even life-threatening.

Two terms are commonly used in blood typing. These are Front typing and back typing.

Front typing: The presence of antigen on red blood cells surface is determined in front type blood typing.

Back type: The presence of antibodies related to the ABO blood group system in plasma is determined in back-type blood typing.

2. Compatibility testing (cross matching).

After the determination of blood types, compatibility testing (cross matching) is performed. There are two types of cross-matching. These are immediate cross matching and full cross matching.

· Immediate cross matching (Minor cross-matching): It is a preliminary test. Mix the recipient’s blood serum with the donor’s red blood cells. Agglutination (clumping) will occur if the recipient’s blood serum contains antibodies against the donor’s red blood cells. These two types of blood will be incompatible. If no agglutination occurs means both blood are compatible. But their further testing is also recommended.

· Full cross-matching (Major cross-matching): Mix the recipient’s blood serum with the donor’s red blood cells. Incubate this mixture at body temperature. Examine the mixture after incubation. Any sign of agglutination or hemolysis indicates incompatibility. Blood transfusion shall not be proceeding. No agglutination or hemolysis indicates compatibility between both types of blood. Blood transfusion can proceed.

Coombs Test

The Coomb test is also called the Direct Antiglobulin test. It is used to detect antibodies in plasma or complement proteins attached to red blood cells. It is used in bloof transfusion medicine to diagnose and manage certain immune mediated hemolytic anemia and to investigate blood transfusion reactions.

There are two types of Coombs test. These are the Direct Coombs Test (Direct Antiglobulin Test) and the Indirect Coombs Test (Indirect Antiglobulin Test).

1. Direct Coombs Test (Direct Antiglobulin Test): It is used to detect antibodies or complement proteins already attached to a patient’s red blood cells. It is used to diagnose immune-mediated hemolytic anemia. caused by antibodies attached to red blood cells' surface. These antibodies may be naturally occurring antibodies or developed for certain reasons such as auto-immune diseases, drug-induced reactions, or incompatible blood transfusion.

Procedure: Collect whole blood from the patient. Separate RBCs from the whole blood. Wash RBCs to remove unattached antibodies or complement protein. Mix washed RBCs with anti-human globulin reagents (Antiglobulin serum). It contains antibodies against human antibodies. If agglutination (clumping) occurs it indicates a positive result. It suggests the presence of antibodies coating RBCs. Agglutination is due to the reaction between Antiglobulin serum and antibodies attached to RBCs.

2. Indirect Coombs Test (Indirect Antiglobulin Test): It is used to detect antibodies present in the recipient’s plasma or serum. These antibodies cause a reaction with the red blood cells of the donor’s blood. It is performed before a blood transfusion to identify antibodies that cause a blood transfusion reaction.

Procedure: Collect recipient plasma or serum. Mix it with red blood cells that have known antigens. Antibodies in the plasma of the recipient will bind with antigens.

Blood Transfusion Reaction:

Blood Transfusion reaction occurs in a person's body receiving blood or blood products. These reactions range from mild to severe.

Classification of Blood Transfusion Reactions: Blood transfusion Reactions are divided into the following two groups.

A. Immune Mediated Reactions

• Immediate Reactions (Within 24 Hours)

  • i. Acute Hemolytic Transfusion Reactions

  • ii. Febrile Non-haemolytic reaction

  • iii. Allergic Reactio

  • iv. Anaphylaxi

  • v. Transfusion Related Acute Lungs Injury (TRALI)

  • · Delayed Reactions (After 24 hours)

• i. Delayed Hemolytic Transfusion Reactions

  • ii. Alloimmunization

  • iii. Post Transfusion purpura

  • iv. Graft versus Host Disease (GVHD)

B. Non-Immune Mediated Reactions

1. Immediate Reactions (Within 24 Hours)

   • i. Bacterial Contamination

   • vii. Transfusion Associated Circulatory Overload

   • viii. Coagulation factor dilution

   • ix. Air embolism

2. · Delayed Reactions (After 24 hours)

   • . Iron overload

Immune Reactions

Immune reactions occur, if the recipient's body identifies foreign substances in the donor’s blood. Under this condition, the recipient body's immune system identifies foreign substances as antibodies and acts against them. This develops antigen antibody reaction. Immune reactions are further classified into two groups: Hemolytic reaction and allergic reaction.

a. Hemolytic reaction: Hemolytic reaction is the destruction of red blood cells after blood transfusion. The hemolytic reaction is mainly due to incompatibility between the recipient’s blood and the donor’s blood. The recipient’s immune system has antibodies against the red blood cells of the donor’s blood. This results in the destruction of transfused RBCs into the donor body. Symptoms of hemolytic reactions are fever, chill, back pain, nausea, decreased blood pressure, rapid heart rate, etc. In severe condition kidney damage and death may occur.

b. Allergic reaction: Allergic reactions occur due to the presence of proteins in transfused blood. Allergic reaction is less severe than hemolytic reaction. Symptoms of allergic reaction are itching, rash, fever, etc. In some cases anaphylaxis may develop that will be life-threatening allergic reaction.

Others Immune Reactions

• Acute Hemolytic transfusion Reactions: The blood recipient body's immune system attacks the red blood cells of received blood. This causes red blood cells rapture. Symptoms are fever, chills, back pain, nausea, hemoglobin excretion in urine, etc

• Febrile Non-Hemolytic Anemia: This is common in blood transfusion. It occurs just after a blood transfusion. It is mainly due to recipient antibody attacks on white blood cells and platelets of blood received. Symptoms are fever, chills, and shivering. Antipyretics are used to control symptoms of it.

• Allergic Reactions: The recipient's immune system reacts to proteins in received blood. This causes antigen-antibody reactions and produces allergies. Symptoms are itching, rash, difficulty in breathing, or anaphylaxis.

• Transfusion Related Acute Lungs Injury (TRALI): It is rare but it is a severe blood transfusion reaction. Antibodies present in received blood react with recipient lung tissues. It causes acute respiratory problems. Symptoms are shortness of breath, cough, and drops in oxygen level. It requires immediate medical treatment.

• Transfusion Associated Circulatory Overload (TACO): It occurs after receiving a large volume of blood or blood products quickly. It causes fluid overload and congestive heart failure (CHF). Symptoms are shortness of breath, cough, and swelling. It is essential to monitor the rate of blood transfusion to prevent TACO.

• Delayed Hemolytic Reaction: It occurs after 24 hours of blood transfusion typically within 2 to 14 days. It occurs due to the recipient's immune system action of red blood cells of received blood. This leads to anemia.

• Graft versus Host Disease (GVHD): It is a rare but severe reaction. Blood donor T-cells attack recipient tissues. It occurs in individuals with low immune systems. It is life life-threatening condition. It requires immunosuppressive therapy.

• Anaphylaxis: It is a severe and life-threatening allergic reaction/. Symptoms are difficulty breathing and a drop in blood pressure.