Detection of Rh Antibodies by Indirect Coombs Method

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

The main aim of the test – is to detect immune IgG class antibodies that can penetrate the placenta and cause the breakdown 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.

Principle of the test: During the indirect Coombs test, the patient's serum is incubated with Rh(D) positive erythrocytes, after which an anti-human (anti-IgG) reagent is added. If there are antibodies in the serum, they bind to the erythrocytes, and the reagent causes agglutination, which indicates a positive reaction.

Recommendations:

• The test is recommended for all RhD negative pregnant women during their first visit and periodically throughout pregnancy.
• It is also performed before blood transfusion for patients with a history of immunization or transfusions to prevent hemolytic transfusion reactions.
• The test is crucial for the development of an Rh immunoprophylaxis plan and for determining the indications for the administration of the immunoglobulin (anti-D).
• The results of the test may be influenced by recent transfusions, pregnancies, and autoimmune diseases.
• No special preparation is required for the test, but it is important to inform the doctor about previous pregnancies, miscarriages, administration of immunoglobulins, or blood transfusions.