What is the most likely cause of an ABO discrepancy where both patient’s cells and serum show no agglutination?

The scenario presented describes a situation in which both the patient's cells and serum demonstrate no agglutination, indicating a strong possibility of an ABO discrepancy. This situation is notably common in young infants, such as a 2-month-old baby, due to the fact that their ABO blood group antigens may not be fully developed. In infants, especially those who are newborns or very young, the presence of maternal antibodies can lead to different serological findings.

Specifically, in a heel stick sample from a young infant, one might expect discrepancies in agglutination patterns because these infants might not yet have developed the expected immune response or adequate levels of their own blood group antigens. Therefore, the lack of agglutination in both cells and serum is especially common in such cases.

This scenario could also be misinterpreted as an issue of serological testing rather than representing an actual mismatch in blood type, which aligns with the characteristics of newborn testing. Thus, the reasoning here is based not on a fault in the tests themselves, but rather on the natural biological condition of the infant being tested.