Clearance of maternal isohemagglutinins from infant circulation (CME)

Non-group O neonates require testing for passively acquired maternal isohemagglutinins for them to receive type-specific red blood cells (RBCs), according to the latest edition of the AABB Standards. A neonate is defined as an infant up to 4 months old in the AABB Standards, and many blood banks tend to stop testing for maternal anti-A and/or anti-B after 4 months of age. In lieu of such testing, group O RBCs are usually transfused to infants up to 4 months of age. This practice can limit the overall supply of group O RBCs available to other patients.

A retrospective study of 1309 infants up to 4 months of age was performed, to assess the age by which passively acquired maternal isohemagglutinins are cleared from infant circulation. Detection of isohemagglutinins was performed by mixing sample sera and observing agglutination, followed by incubation and addition of anti-immunoglobulin anti-human globulin (antiglobulin test phase).

The data show that 6.4% of infants up to 1 month of age had maternal isohemagglutinins, while none of the infants ranging from 2 to 4 months of age had maternal isohemagglutinins in their sera.

Maternal isohemagglutinins are rare after the first month of life and patients who are at least 2 months old can safely receive ABO type-compatible RBC units without testing for passively acquired maternal anti-A and/or anti-B.