Resolving variable maternal D typing using serology and genotyping in selected prenatal patients.
RhIG prophylaxis for D- pregnant women prevents hemolytic disease of the newborn and typically depends on results of serologic D typing. Interpretation and follow-up of weak D serology is variable. Recent recommendations promote genotyping for RHD status determination in those with weak D serology. Canadian Blood Services performs comprehensive serologic prenatal testing in four provinces. Genotyping is used to determine D typing in patients with weak D.



A serologic algorithm identified which patients require genotyping for RHD determination. Genotyping was performed on one of two commercially available platforms.



Only 0.4% of D- patients met criteria for genotyping. Sixty-one percent were weak D Type 1, 2, or 3. Thirty percent had a partial or weak D other than Type 1, 2, or 3. Eleven had variants which remained unresolved. Seventeen were D+ and four were D-.



Genotyping of patients with weak D serology led to an identified genotype in most patients. RhIG administration was avoided in 66% who were weak D Type 1, 2, or 3 or were D+. The use of a serologic algorithm to select patients for RHD genotyping identifies a majority of patients with weak D types not at risk for alloimmunization. This approach limits the number of genotyping investigations and the cost of providing classification for weak D types.
Canadian Blood Services, Canada.
Gwen
G
Clarke
Canadian Blood Services, Canada.
Judith
J
Hannon
Canadian Blood Services, Canada.
Philip
P
Berardi
Canadian Blood Services, Canada.
Gerri
G
Barr
Canadian Blood Services, Canada.
Jacqueline
J
Cote
Canadian Blood Services, Canada.
Robert
R
Fallis
Canadian Blood Services, Canada.
Ted
T
Alport
Canadian Blood Services, Canada.
Debra
D
Lane
Canadian Blood Services, Canada.
Tanya
T
Petraszko
Progenika, Inc.-Grifols, San Marcos, Texas.
Gorka
G
Ochoa
Canadian Blood Services, Canada.
Mindy
M
Goldman
D000328:Adult; D000465:Algorithms; D001788:Blood Grouping and Crossmatching / Q000145:classification* / Q000379:methods; D004899:Erythroblastosis, Fetal / Q000517:prevention & control*; D005260:Female; D005838:Genotype; D006801:Humans; D007518:Isoantibodies / Q000032:analysis; D018579:Patient Selection; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D012204:Rh-Hr Blood-Group System / Q000276:immunology*; D018029:Rho(D) Immune Globulin / Q000032:analysis*; D055815:Young Adult
D007518:Isoantibodies; D012204:Rh-Hr Blood-Group System; D018029:Rho(D) Immune Globulin