Indirect Coombs Test in Dehradun

What is a Indirect Coombs Test?

The indirect Coombs test looks for antibodies against red blood cells circulating free in the plasma, rather than already attached to cells. It has two major applications. The first is in pregnancy. An Rh-negative woman carrying an Rh-positive baby can be exposed to the baby's red cells, most often at delivery but also with bleeding, miscarriage, amniocentesis or abdominal trauma, and may then produce anti-D antibodies. Those antibodies do not usually affect the current pregnancy but cross the placenta in a subsequent one and destroy the next baby's red cells, causing haemolytic disease of the newborn. Detecting them allows the pregnancy to be monitored, and, far better, preventing them with anti-D immunoglobulin given at defined points renders the whole problem largely avoidable. The second application is transfusion safety: before blood is given, the recipient's plasma is screened for antibodies that would attack donor cells, and this test is the basis of cross-matching. It is the same laboratory principle serving two quite different clinical purposes.

Why take this test?

An indirect Coombs test is advised for every Rh-negative pregnant woman as part of routine antenatal care, typically at booking and again around 28 weeks, to detect whether antibodies have formed and to guide anti-D prophylaxis. It is repeated after any event that could cause fetal-maternal bleeding, including miscarriage, termination, amniocentesis, external cephalic version, abdominal trauma or antepartum bleeding. It is used before any planned transfusion as part of cross-matching, and in anyone with a history of transfusion reactions or known red-cell antibodies. It is also relevant for a woman with a previous baby affected by haemolytic disease. If you are Rh negative, the single most important thing is not the test but the anti-D injection your obstetrician arranges at the right times, since prevention is far more effective than monitoring an antibody that has already formed.

• Routine antenatal care in every Rh-negative pregnant woman
• After miscarriage, termination, amniocentesis or abdominal trauma
• Antepartum bleeding in an Rh-negative woman
• Before a planned blood transfusion, as part of cross-matching
• A history of transfusion reactions or known red-cell antibodies
• A previous baby affected by haemolytic disease of the newborn

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