Which test is commonly positive in cases of ABO incompatibility?

In cases of ABO incompatibility, the Direct Coombs Test is commonly positive. This test detects antibodies that are attached to the surface of red blood cells, which is a crucial aspect of determining the presence of hemolytic disease resulting from blood group incompatibility.

When an infant has ABO incompatibility, the mother's immune system may produce IgM antibodies against the blood group antigens of the infant, leading to hemolysis of the infant's red blood cells. The Direct Coombs Test identifies these attached antibodies, confirming that the infant's red blood cells are being targeted and destroyed by the immune response initiated by the mother.

Other tests like the Indirect Coombs Test primarily assess for unbound antibodies in the serum and are not specifically aimed at detecting those antibodies on red blood cells. A Complete Blood Count can provide useful information about the infant's hematologic status but does not specifically diagnose ABO incompatibility. Hemoglobin Electrophoresis is used to identify different hemoglobin types and is not relevant in testing for ABO incompatibility. Therefore, the Direct Coombs Test is the key test that clearly demonstrates the serological response associated with ABO incompatibility in neonates.