A specimen of cord blood is submitted to the transfusion service for routine testing. Among the results obtained, which antibody is the most likely cause of a positive direct antiglobulin test?

In the context of cord blood testing, the most common antibody associated with a positive direct antiglobulin test (DAT) is anti-c.

When a DAT is performed, it detects the presence of antibodies or complement proteins bound to the surface of red blood cells. In the case of cord blood, the most likely source of antibodies is from the mother, especially when there is an Rh incompatibility or a situation involving minor blood group antigens.

Anti-c is one of the antibodies frequently found in cases of hemolytic disease of the newborn (HDN), especially when the mother is sensitized to this antigen. This type of isoimmunization can occur during pregnancy if the mother has a different Rh or minor blood group type than the fetus, leading to the production of antibodies against the fetal red blood cells.

Anti-A and anti-D can also lead to a positive DAT if the mother has those antibodies, but anti-c is particularly noted for its association with cord blood samples and HDN. Therefore, in the scenario of a routine cord blood test where a positive DAT result is observed, anti-c is the most likely antibody responsible.

Anti-C is less common in terms of causing DAT positivity compared to anti-c and is not as frequently implicated in