Detection of Rh Antibodies by Indirect Coombs Method

Detection of Rh antibodies by Indirect Coombs (Coomb’s) method is a serological test designed to detect the presence of antibodies against erythrocyte antigens in the patient's blood serum or plasma. This test is most commonly used during pregnancy or before blood transfusions to identify an immune response to Rh or other erythrocyte antigens. It allows early detection of a possible Rh conflict between the mother and the fetus.

The main goal of the test is to detect immune IgG class antibodies capable of crossing the placenta and causing the destruction of fetal or newborn erythrocytes. The test has the greatest clinical significance in assessing the risk of hemolytic disease of the newborn (HDN) when an RhD negative mother carries an RhD positive fetus. The formed antibodies can attack the fetal erythrocytes, causing anemia, jaundice, or even fetal death.

Test principle: During the Indirect Coombs test, the patient's serum is incubated with Rh(D) positive erythrocytes, and then an antihuman (anti-IgG) reagent is added. If antibodies are present in the serum, they attach to the erythrocytes, and the reagent causes agglutination, indicating a positive reaction.

Recommendations:

• The test is recommended for all RhD negative pregnant women at the first visit and periodically during pregnancy.
• It is also performed before a blood transfusion in patients with previous immunizations or transfusions to prevent hemolytic transfusion reactions.
• The test is crucial for developing an Rh immunoprophylaxis plan and determining the indications for immunoglobulin (anti-D) administration.
• Recent transfusions, pregnancies, and autoimmune diseases can affect the test results.
• No special preparation is required for the test, but it is important to inform the doctor about previous pregnancies, miscarriages, immunoglobulin administration, or blood transfusions.