Acrobat
MS WordPerinatologist Corner - C.E.U/C.M.E. Modules
Antibody Screen Positive: Rh Disease and Other Atypical Antibodies
Sponsored by The Indian Health Service Clinical Support Center
2. Rh Disease and Other Atypical Antibodies
Step 2. Background
History
“Hydrops fetalis” and “icterus gravis” as a cause of stillbirth and neonatal death were first described in the 1600’s. In 1940 Landsteiner and Weiner performed the landmark work that led to the development of safe blood transfusion, as well as elucidating the cause of “erythroblastosis fetalis” or hemolytic disease of the newborn, what they called “the rhesus monkey antibody”. The next major breakthrough came in 1967 with the development of rhesus immune globulin (RhIg or “RhoGam”) as the highly effective means to prevent this once major perinatal disease. Despite the availability of effective prophylaxis, rhesus hemolytic disease continues to occur however.
Why are so few Native Americans Rh positive?
The genetic locus for “Rh” is on the short arm of chromosome 1. Three genes (CDE), each with two alleles (C/c, D/null, E/e), are present at this locus. The final gene product, which has multiple genetic determinants, is present on the red cell surface and determines whether one is Rh positive (D antigen present) or not. Similarly there are determinants for the C and E antigens, to be discussed later. Rh negativity is typically a Caucasian mutation, approximately 15% of Caucasians being Rh negative.
By comparison only 1-2% of Native Americans are Rh negative, and only 0.01% of Asians. (See Table 1) The similarity between rates in Native Americans and Asians would be In keeping with the Bering Land Bridge theory of anthropologic migration patterns.
Approximately 45% of Rh positive individuals are homozygous (D/D), and 55% are heterozygous (D/null, or D/d for ease of notation). By definition, Rh negative individuals are homozygous for the “null set” (no D antigen).
Table 1: Incidence of the Rh Negative Blood Group in Various Populations
Population |
Incidence |
Chinese and Japanese |
1% |
North American Indian and Inuit |
1 - 2% |
Indo-Eurasian |
2% |
African American |
4 - 8% |
Caucasian |
15 - 16% |
Basque |
30 - 35% |
Source: Table 1
ObFocus.com – Management of Isoimmunization
For more on why AI/AN have such different prevalence(s) of antibodies
Serology: Bergen County Technical Schools
