Anti Human Globulin

Anti-Human Globulin (AHG) – Coombs Reagent for Blood Testing

Anti-Human Globulin (AHG), also known as Coombs reagent, is a specialized laboratory reagent used in immunohematology and blood compatibility testing. It is designed to detect antibodies or complement proteins that have bound to red blood cells (RBCs) but do not cause visible agglutination. AHG plays a crucial role in diagnosing hemolytic disorders, ensuring safe blood transfusions, and identifying blood group incompatibilities.

Types of Anti-Human Globulin Tests

AHG is used in two primary tests:

1. Direct Antiglobulin Test (DAT) – Direct Coombs Test

   • Detects antibodies or complement proteins that are already attached to RBCs inside the body.
   • Used to diagnose autoimmune hemolytic anemia, hemolytic disease of the newborn (HDN), drug-induced hemolysis, and transfusion reactions.

2. Indirect Antiglobulin Test (IAT) – Indirect Coombs Test

   • Detects free antibodies in a patient’s serum that may react with RBCs.
   • Used for pre-transfusion compatibility testing, antibody screening, and crossmatching in blood banks.

How AHG Works

1. In a Direct Coombs Test (DAT), patient RBCs are washed and mixed with AHG. If antibodies or complement proteins are present on the RBC surface, AHG causes visible agglutination, confirming a positive reaction.
2. In an Indirect Coombs Test (IAT), patient serum is incubated with test RBCs, followed by AHG addition. If antibodies in the serum bind to the test RBCs, agglutination occurs, indicating the presence of clinically significant antibodies.

Applications of Anti-Human Globulin

• Blood Transfusion Compatibility – Ensures that donor and recipient blood are compatible, preventing transfusion reactions.
• Hemolytic Disease of the Newborn (HDN) Diagnosis – Detects maternal antibodies attacking fetal RBCs due to Rh incompatibility.
• Autoimmune Hemolytic Anemia Diagnosis – Identifies antibodies causing the body to destroy its own RBCs.
• Pre-Transfusion Testing – Screens for unexpected antibodies in patients receiving blood transfusions.