4022. Coombs test (direct)

The direct Coombs test is an antiglobulin test that detects antibodies attached to the surface of red blood cells circulating in the bloodstream. It is used to detect immune hemolysis, particularly in autoimmune hemolytic anemia, hemolytic disease of the newborn, transfusion reactions, and drug-induced hemolysis.

The direct Coombs test is an antiglobulin test that detects anti-erythrocyte antibodies or complement components attached to the surface of red blood cells.

The direct Coombs test helps identify and confirm the immune origin of hemolysis, particularly in the following clinical conditions:

• Autoimmune hemolytic anemia (AIHA).
• Alloimmune hemolytic reaction – in cases of incompatibility during blood transfusion, when the recipient's antibodies destroy the donor red blood cells.
• Hemolytic disease of the newborn (HDN).
• Drug-induced immune hemolysis.
• Post-transplant conditions.

A negative reaction does not rule out an immune disorder, as antibodies can be free in the plasma (not bound to red blood cells). To detect these, an indirect Coombs test is performed.

When?

• In case of decreased hemoglobin levels accompanied by elevated LDH, indirect bilirubin, and decreased haptoglobin.
• If an immune reaction is suspected after a blood transfusion.

Who?

• Patients with symptoms of hemolytic anemia (jaundice, dark urine, splenomegaly).
• Newborns at risk of hemolytic disease due to Rh incompatibility or ABO incompatibility.
• Post-transplant patients or those with hematological malignancies, especially if red blood cell lysis is suspected.

• Venous blood

In order to exclude factors that may affect the test results, we recommend to follow the preparation rules: