Considering the ABO typing results, what is the most likely cause of the discrepancy observed?

In ABO typing, discrepancies can arise from various factors, and understanding the underlying causes is crucial for accurate interpretation. A cold autoantibody is often implicated in discrepancies during ABO typing because it can react with red blood cells at lower temperatures, potentially leading to false results.

Cold autoantibodies typically belong to the IgM class and are reactive at low temperatures, which can mask the specific antigen-antibody interactions expected during the typing process. When these autoantibodies are present, they may bind nonspecifically to the red blood cells, causing a discrepancy in the observed typing results. This can result in a weak or false positive reaction, leading to confusion regarding the true ABO group of the sample.

By contrast, the other options may lead to discrepancies but in different contexts. For instance, a cold alloantibody is usually directed against specific antigens on transfused cells from another individual, which is less common in routine ABO typing scenarios. An A2 with anti-A1 involves specific blood group variations that could also create discrepancies but are not as general as cold autoantibodies. The acquired-A phenomenon is associated with individuals who have A-like antigen expressions due to certain medical conditions, but this is also a less frequent cause in straightforward ABO typing discrepancies