Clinical Pathology Abstracts, 8/17

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Outcomes of Blood Group Antigen Matching Influence on Gestational Outcomes study

The approach to red blood cell matching of females of childbearing potential to prevent alloimmunization varies among health care centers. Some centers will use extended matching to prevent RBC alloimmunization to non-D RBC antigens to decrease the future pregnancy risk of hemolytic disease of the fetus and newborn (HDFN). This may include K, C, E, or c matching. The authors conducted a multinational retrospective study of women with offspring affected by severe HDFN requiring neonatal transfusion or intrauterine exchange, or both, to determine if blood bank policies of prospective antigen matching are effective in decreasing the risk of HDFN. They compared mothers treated at centers that provide extended antigen-negative RBCs (Match, five centers) and those that do not (NoMatch, nine centers). The results showed that 293 mothers had at least one affected pregnancy: 179 at Match centers and 114 at NoMatch centers. Eighty-three percent of the alloimmunizations were due to a previous pregnancy, three percent to transfusion, and 14 percent undetermined. Only 50 mothers received transfusions; 13 at Match and four at NoMatch centers had HDFN due to anti-K. Most of the anti-K HDFN (12 of 13) cases at Match centers were due to K+ paternal antigen status. The study concluded that mothers at the Match centers do not appear to be protected from HDFN due to K, C, c, and E antibodies. However, a limitation of the study was the low number of females of childbearing potential who received transfusions and the lack of uniformity between matching policies. The authors concluded that these results showed that the causal stimulus of antibodies that cause HDFN is predominantly from a previous pregnancy. The authors were unable to show a positive effect with extended RBC antigen matching. They also concluded that as more blood centers work to provide RBC antigen typing or genotyping data on RBC units to transfusion services, the feasibility of providing matched units for HDFN prevention, even at small numbers, will improve.

Delaney M, Wikman A, van de Watering L, et al. Blood Group Antigen Matching Influence on Gestational Outcomes (AMIGO) study. Transfusion. 2017;57:525–532.

Correspondence: Dr. Meghan Delaney at meghand@bloodworksnw.org