(P-TS-94) RhD alloimmunization rates of RhD-negative females who received O-positive whole blood on medical flights

Whole blood transfusions during medical flights play a crucial role, yet the selection of compatible blood poses a critical challenge. While O-negative whole blood is the most compatible, its supply is limited and if the only prestorage platelet sparing leukoduction system is used, it has a 21 day outdate resulting in flight services using O-positive whole blood. The primary objective was to assess frequency of females receiving whole blood who were later determined to be Rh (D) negative and, if possible, record sensitization events. 

Study

Design/Methods: The primary objective was to determine the presence or absence of anti-RhD antibodies in females of child bearing age who received group O Rh (D) positive whole blood during emergency air ambulance transport. Patient data including names, transport dates, dates of birth, and the names of the receiving hospitals of all female patients, were obtained, after human subjects committee approval, from a medical flight company that initiated the use of O-positive whole blood in March of 2019.  Our blood center provides blood to multiple sites which vary with the furthest site about 3 hours away and therefore, the economics and logistics limit deliveries to every other week. The air ambulance service provided the number of males who received O-positive whole blood during the same time frame. Following this, the hospitals receiving female patients were contacted, requesting information regarding each patient’s blood type. If the patient was identified as having an RhD-negative blood type, further information was requested about evidence of sensitization such as a positive antibody screen. All data retrieval and communication was conducted following approval of Institutional Review Boards, including several for the receiving hospital systems (over 40 receiving hospitals in all!).

Results/Findings: Of 407 O-positive whole blood units transfused on emergency medical flights (one unit/patient), 119 were female (29%) and of these, 14 are known to be RhD-negative and only 6 were of childbearing age. Of the female Rh (D) negative recipients, only a single recipient is known to be sensitized to RhD and the remainder had no subsequent testing at the hospital where they received their emergency care.

Conclusions: Given the continual strain on the Group O Rh (D) negative blood supply, this retrospective study provides confirmatory support for the policy of providing Rh (D) positive units for air ambulances. It further highlights the human subjects challenges of data collection across hospital systems.