Rh-hr Genotype With ABO Grouping

Whole blood

4 mL

1 mL

Lavender-top (EDTA) tube

Determine ABO blood grouping and most probable zygosity for D(Rh_o) antigen. Zygosity for C, E, c, and e antigens is also determined. Paternal typing may aid in the prediction of Rh hemolytic disease of the newborn.

Abnormal plasma proteins, potent cold autoagglutinins, positive direct antiglobulin test, and in some cases bacteremia may interfere with test interpretation. Variable testing results may be observed with partial antigens which are rare variants of the Rh_o(D) antigen.

Hemagglutination

When a woman of childbearing age has anti-D, it is important for prognostic purposes to determine the probability that her husband is homozygous or heterozygous for the gene determining the D antigen. If a prenatal patient is Rh-negative and the father of her fetus is homozygous for D, the child will always be Rh positive. Approximately 50% of the children of a heterozygous father will be Rh-negative. Testing to determine zygosity involves testing the subject's red blood cells for D, C, E, c, and e antigens. The results of this testing are referred to as the Rh phenotype. The Rh phenotype is used to determine a “most probable” zygosity for D based upon correlation of these results with a frequency chart detailing most probable Rh genotypes. In the case of D, this must be done indirectly since there is no detectable allele for this gene. In the case of the alleles C and c and the alleles E and e, the zygosity of these genes may be directly determined from the phenotyping results. Rh phenotyping of the father may also be helpful for evaluating the potential for hemolytic disease of the newborn in the presence of maternal antibodies to C, c, E, or e antigens. See table.