Extending antigen-matching protocols lowers odds for hemolytic disease of fetus, newborn

Key takeaways:

• Alloimmunization rates were 6.2% for women matched to ABO and Rhesus D and 1.9% for women also matched for c, E and K antigens.
• Extended antigen matching was tied to less alloimmunization vs. standard protocol.

Extending routine donor-recipient matching to include Rhesus c, E and K antigens was tied to lower odds for hemolytic disease of the fetus and newborn vs. standard ABO blood type and Rhesus D antigen matching, researchers reported.

“U.S. National guidelines recommend that all blood products be routinely phenotyped for ABO blood type and Rhesus D. Additional antigen matching to include Rhesus c, E and Kell typically has been reserved for patients at highest risk for chronic allogenic transfusion such as those with sickle cell disease, thalassemia and myelodysplasia,” Ronan P. Sugrue, MBBChB, MPH, maternal-fetal medicine specialist in the department of obstetrics and gynecology at Duke University School of Medicine, and colleagues wrote. “Women younger than age 50 years, however, are at elevated risk of alloimmunization and the consequences of alloimmunization if pregnancy occurs can be substantial, prompting several high-income countries to offer routine c, E and Kell matching in this population.”

Sugrue and colleagues conducted a systematic review and meta-analysis, published in Obstetrics & Gynecology, identifying 10 studies published from March 2023 to April 2024. All studies reported alloimmunization as the primary outcome among women who received red blood cells matched for ABO blood type and Rhesus D antigen or additional c, E and K antigen matching.

Among 91,221 women who received transfusions, 44.1% received additional red blood cell antigen matching for c, E and K antigens. Follow-up antibody testing ranged from 6 to 18 months after transfusion. Overall alloimmunization rate was 6.2% for women matched to ABO blood type and Rhesus D antigen only and 1.9% for women also matched for c, E and Kell antigens.

Extending antigen matching to include c, E and K antigens was associated with less alloimmunization vs. standard protocol (OR = 0.37; 95% CI, 0.2-0.69). Researchers observed this association even when excluding chronically transfused women (OR = 0.65; 95% CI, 0.54-0.79) and for women alloimmunized to c, E or K antigens (OR = 0.29; 95% CI, 0.18-0.47).

“These findings may ultimately inform changes to national guidelines on protocols for donor-recipient matching of blood products prescribed to people with pregnancy potential in the United States and elsewhere,” the researchers wrote.