What is the result of anti-A: 0 in a blood typing test likely indicating?

A result of anti-A: 0 in a blood typing test strongly suggests that the blood group is O. In the ABO blood group system, individuals with type O blood lack A and B antigens on the surface of their red blood cells. As a result, when anti-A serum, which contains antibodies against the A antigen, is added to a sample of type O blood, there will be no reaction, leading to the observation of "0" (or no agglutination).

In contrast, type A blood would show agglutination when exposed to anti-A due to the presence of A antigens. Similarly, type B blood would react with anti-B, and type AB blood would agglutinate with both anti-A and anti-B. Thus, the lack of reactivity with anti-A serum is definitive for identifying group O blood.

Mixed field reactions typically indicate the presence of more than one population of red blood cells, which could suggest some form of chimerism or blood transfusion. Group A1 refers to individuals with A antigens that can react with anti-A; therefore, it cannot be correct in the context where anti-A shows no interaction. Additionally, the presence of B antigens would generate a positive result with anti