Prenatal diagnosis of Kell blood group genotypes: KEL1 and KEL2.

OBJECTIVE

Our purpose was to devise diagnostic test(s) that determine fetal KEL1 and KEL2 genotypes.

STUDY DESIGN

KEL1 and KEL2 polymorphisms are due to a single C to T base substitution at nucleotide 698 of exon 6 of KEL. This allowed us to develop two polymerase chain reaction tests that distinguish KEL1/1 and KEL2/2 homozygotes and KEL1/2 heterozygotes. The first test uses a Bsm I restriction fragment length polymorphism in a genomic deoxyribonucleic acid polymerase chain reaction product containing the single base polymorphism, and the second test uses allele-specific primers to distinguish KEL1 and KEL2 genotypes. These tests were applied in a blind study to 15 amniotic fluid deoxyribonucleic acid samples. The corresponding KEL1 and KEL2 fetal red blood cell phenotypes were determined serologically. The tests were also applied to two families in which the mothers had antibodies to KEL1.

RESULTS

In all cases results of analysis of Kell genotypes from the amniotic fluid deoxyribonucleic acid samples agreed with the fetal red blood cell Kell phenotypes. The tests were also successfully used to determine fetal Kell genotype by use of peripheral blood deoxyribonucleic acid.

CONCLUSION

Two polymerase chain reaction-based tests can be used for prenatal diagnosis of KEL1 and KEL2 genotypes; these procedures should prove useful in the proper management of Kell-sensitized pregnancies.