Clinical Specificity of RBC Alloantibodies Studied in Pregnant Women

Maternal red cell immunoglobulin G (IgG) antibodies can cross the placenta and cause hemolysis of fetal red cells in case of antigenic differences between maternal and fetal red blood cells (RBCs), leading to hemolytic disease of the fetus and newborn (HDFN).

Although the incidence of anti-D associated HDFN has drastically reduced with Rh immune globulin prophylaxis, HDFN due to other maternal red cell alloantibodies still remains a concern. Prevalence and specificities of clinically significant red cell alloantibodies in pregnant females have rarely been reported in the USA.

Medical Laboratory Scientists at the Beaumont Hospital (Royal Oak, MI, USA) conducted a retrospective chart review to determine the prevalence and specificity of clinically significant red cell alloantibodies in pregnant females who delivered at the hospital between May 1, 2017, and December 31, 2017. A total of 4,545 pregnant females with a valid ABO/RhD type and valid red cell antibody screen were included. ABO/RhD typing and antibody screening were performed using the gel card methodology with automated blood bank analyzers Ortho ProVue, whereas the specificity of antibodies was identified with indirect antiglobulin testing using the manual gel card methodology.

The team reported that out of the 4,545 females, 440 had a positive red cell antibody screen. Of these 440 females, 34 had clinically significant alloantibodies, giving an overall prevalence of 0.74%. Anti-E was the most frequently identified significant alloantibody followed by anti-K. The most prevalent significant alloantibodies in RhD positive and RhD negative females were anti-E and anti-K, respectively. Significant association was found between RhD type and the presence of clinically significant alloantibodies amongst females with a positive antibody screen. Out of 34 females with clinically significant red cell alloantibodies, six (17.6%) females had more than one clinically significant alloantibody; all of them being multigravida, indicating a higher risk of multiple red cell alloimmunization with subsequent pregnancies.

The authors concluded that anti-E and anti-K were the two most frequently identified clinically significant red cell alloantibodies in their study population. The findings of the study aim to re-emphasize the importance of screening and detection of red cell alloantibodies early in pregnancy to help identify and appropriately manage high-risk pregnancies, in addition to increasing the understanding amongst pregnant females about these antibodies and the associated risk of HDFN. The study was published on August 13, 2019, in the Journal of Blood Medicine.

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