COOMBS INDIRECT (ICT), SERUM

Coombs Indirect (ICT), Serum

What it is

The Coombs Indirect Test (Indirect Antiglobulin Test, or Indirect Coombs Test – ICT) is a blood test performed on serum that detects free antibodies against red blood cells circulating in the bloodstream. Unlike the direct test, which identifies antibodies already attached to red cells, the ICT looks for unbound antibodies in the serum that could bind to transfused red cells or a fetus’s red cells during pregnancy.

Uses

The Indirect Coombs Test is commonly used in blood compatibility testing before transfusions, in prenatal screening to check for maternal antibodies against fetal red blood cells (Rh incompatibility), and in organ transplant evaluations. It helps prevent transfusion reactions and hemolytic disease of the newborn (HDN).

Symptoms That May Lead to the Test

This test may be ordered if you are scheduled for a blood transfusion, during pregnancy as part of routine antenatal care, or if your doctor suspects immune-related complications. In pregnancy, it is especially important for Rh-negative mothers, as antibodies against Rh-positive fetal blood can develop and cause complications in the baby.

Abnormal Results

Positive ICT: Indicates that antibodies against red blood cells are present in the serum. This could suggest a risk of transfusion reaction, maternal-fetal blood group incompatibility, or alloimmunization due to previous transfusions or pregnancy.

Negative ICT: Suggests no significant antibodies detected, meaning safe compatibility for transfusion and lower risk of hemolytic disease in pregnancy.

Risks

The test requires only a routine blood draw. Risks are minimal and limited to slight discomfort, bruising, or dizziness at the puncture site, all of which are temporary.