RESUMO
<p><b>OBJECTIVE</b>To investigate the similarity and difference in blood group serology and molecular biology of A2 and A2B phenotypes between healthy blood donors and patients.</p><p><b>METHODS</b>The A and AB phenotypes were screened with anti-A1. Exons 1 to 7 and intron 6 of the ABO gene were analyzed with polymerase chain reaction-sequence-based typing (PCR-SBT) method. The blood type was determined by referring to the Blood Group Antigen Gene Mutation Database (BGMUT).</p><p><b>RESULTS</b>Among 7111 tested individuals, 75 were assigned as A2 or A2B phenotypes. However, only 28 individuals still belonged to the A2-related allele group based on genetic analysis. Among these, A205/B101 was the most common genotype. Among those non-A2-related alleles, A102/B101 was the most common genotype. Based on serologic testing, there was an imbalance between the A2 and A2B subgroups. In both donor group and patient group, the proportion of A2B was significantly higher than that of the A2. There were statistical differences between different groups (χ² = 64.613, 33.137, 34.963, P< 0.01). At the gene level, the imbalance still existed in both the overall population and the donor group, though there was a statistical difference between the two (χ² = 17.678, 14.157, P< 0.01). The same imbalance did not exist in the patient group (with continuous correction, χ² = 2.351, P= 0.125).</p><p><b>CONCLUSION</b>The concordance rate for blood type determined by serology and genetic analysis has been low and deserves attention. For A2 and A2B phenotypes by serological screening, A102/B101 was the most common gene among non-A2-related alleles. Further study is needed to clarify this phenomenon.</p>