Experts Question RhD-Positive Whole Blood for Patients With Reproductive Potential When Compatible Products Are Available

Transfusion medicine, obstetric and ethics experts are questioning the use of RhD-positive whole blood for RhD-negative or RhD-unknown patients with reproductive potential when RhD-compatible products are available.

In a clinical perspective published in Obstetrics & Gynecology, Jeremy W. Jacobs, MD, MHS, of Vanderbilt University Medical Center, and coauthors argued that two recent randomized trials showing no survival advantage for prehospital whole blood have weakened the rationale for accepting the reproductive risk.

Low-titer group O whole blood is usually RhD-positive because RhD-negative whole blood is scarce. For RhD-negative or RhD-unknown patients with reproductive potential, exposure to RhD-positive red cells can cause anti-D alloimmunization, which can place future pregnancies with an RhD-positive fetus at risk for hemolytic disease of the fetus and newborn. The authors noted that reported alloimmunization rates among injured RhD-negative patients range from 7.8% to 42.7%.

For patients who develop anti-D, later pregnancies may require additional monitoring and specialist care, including serial antibody testing, fetal surveillance and, in severe cases, intrauterine transfusion. According to the researchers, accepting this risk has depended largely on the belief that whole blood improves survival enough to justify it.

According to Jacobs and his colleagues, the SWiFT and TOWAR trials have tested that premise. SWiFT randomized 942 patients with suspected major traumatic hemorrhage across 10 air ambulance services in England to prehospital whole blood or standard care with red cells and plasma. Death or massive transfusion within 24 hours occurred in 48.7% of patients receiving whole blood and 47.7% of those receiving standard care. TOWAR included 1,020 patients at 44 U.S. air medical bases and found no reduction in 30-day mortality with whole blood compared with component therapy. Mortality was 25.9% with whole blood and 20.5% with component therapy (adjusted odds ratio, 1.24; 95% CI, 0.87 to 1.76). Neither trial demonstrated superiority for whole blood, and whole blood did not reduce the need for additional red cells, plasma or platelets.

The authors recommended that patients with reproductive potential default to RhD-negative products when compatible products are immediately available, until their RhD type is confirmed. They emphasized, however, that transfusion should not be delayed for patients with life-threatening hemorrhage and that RhD-positive whole blood may still be necessary when compatible products cannot be provided without delaying lifesaving transfusion, including in some austere or military settings.

When RhD-incompatible transfusion occurs, the authors recommended standardized, cost-free follow-up, including documentation of the exposure, counseling about future pregnancies and transfusions, and antibody screening at about 14 weeks after exposure and no later than six months. Screening should be repeated during subsequent pregnancies, they said.

The authors also called for trauma trials to reconsider RhD product selection for participants with reproductive potential and to ensure follow-up when RhD-incompatible exposure occurs.