P1/P2 genotyping of known and novel null alleles in the P1PK and GLOB histo-blood group systems.

The rare but clinically important null phenotypes of the P1PK and GLOB blood group systems are due to alterations in A4GALT and B3GALNT1, respectively. A recently identified single-nucleotide polymorphism in Exon 2a of A4GALT predicts the common P1 and P2 phenotypes but rare variants have not been tested