P antigen frequency is very low in the Chinese population. However, the presence of anti-P1PPk
(anti-Tja) is a huge risk for patients undergoing clinical transfusions and recurrent abortions. This report aims to describe p antigen and anti-Tja serological test features and suggests ways in which we may better identify the p antigen. Polymerase chain reaction was used to amplify A4GALT and B3GALNT1, which were then analysed for polymorphisms using Sanger sequencing. The A4GALT sequence results revealed c. 547-548delAT (HE818933), which resulted in a frame shift at aa 183 stopping at aa 281 (M183fs, 281X). Compared with the reference sequence, B3GALNT1 did not show any variations in any of the subjects assessed. Eggs from Columba livia were used in the neutralised P substance test, but failed to neutralise anti-Tja. The serological test and molecular analysis confirmed that the P blood antigens are caused by A4GALTc. 547-548 AT deletion, and the neutralised P substance test cannot identify anti-PP1Pk from RBC alloantibodies against high frequency antigens.