Is it OK to Transfuse ABO and Rh Mismatched Platelets?

by William Crews, MD

Many factors put demands on platelet availability in our facility and our community. These include the need for quality control and bacterial testing, the short shelf life, an increase in utilization over recent years, and loss of donors with new regulations. For all these reasons we encourage transfusion services and transfusing physicians to consider the use of non-ABO matched platelets in adult patients as described below whenever necessary and reasonable.

Platelets are often transfused regardless of their ABO group because ABO antigens are only weakly expressed on platelets. Most adults have soluble A or B antigenic substances in their blood that are capable of neutralizing the antibodies in small amounts of ABO-incompatible plasma, such as one platelet transfusion. For high-risk patients (neonates and young pediatric patients, stem cell transplant patients, and organ transplant patients) a special effort to use plasma-compatible platelets is preferred to prevent possible hemolysis.

It is known that ABO major incompatibility platelet transfusion is associated with lower rates of post-transfusion corrected count increment and accelerated destruction of platelets in the recipient. But studies have shown the transfusion of PLTs with major ABO-incompatibility is equally effective in preventing clinical bleeding compared to ABO-identical and platelets with ABO-minor incompatibility. If a patient has an indication to receive a platelet transfusion and an ABO compatible platelet is not immediately available, the benefit of transfusing an ABO incompatible platelet may outweigh the risk of waiting for a compatible platelet. Even in high-risk patients this is possible since any anti-A or anti-B would be diluted into 2 to 3 L of recipient plasma in adult patients. In pediatric patients, if a major ABO incompatible transfusion is unavoidable, the unit should have the plasma removed before transfusion as an alternative approach. Close monitoring of the patient should take place to ensure the incompatible plasma does not cause hemolysis.

Platelets do not express Rh antigens on their surface, and with the majority of platelets being collected by apheresis technology, the amount of (passenger red cells) contaminating red cells are felt to be negligible enough that anti-D alloimmunization after RhD-incompatible platelet transfusion does not warrant serious concern. The red cell content in apheresis platelets is estimated to be less than 0.001 mL per unit. An exception for RhD negative females of childbearing age is made by some clinicians. Although the cases of documented immunization which have been documented for patients getting a low number of modern apheresis platelets is very low. Administration of the lowest dose of RhIG is sufficient for one apheresis platelet if deemed necessary.

Summary of Platelet component selection

• ABO type of platelets:
  ° ABO-identical platelets can be given if plentiful, especially for smaller patients or for repeated transfusions
  ° ABO-mismatched platelets may result in lower corrected count increments but this difference is not usually clinically significant
  ° ABO-incompatible plasma in platelets may cause a positive DAT or may rarely cause hemolysis

• Rh type of platelets:
  ° Rh negative males and females past childbearing age may receive Rh positive apheresis platelets if Rh negative platelets are in short supply
  ° Females of childbearing potential can receive Rh-positive platelets if needed. Although, RhIG should be given for pooled platelets and may be given following apheresis platelets, especially if multiple units are used.
  ° Rh negative platelets may be given to Rh negative patients if plentiful

References:
1) Valsami S, Dimitroulis D, Gialeraki A, Chimonidou M, Politou M, Current trends in platelet transfusions practice: The role of ABO-RhD and human
leukocyte antigen incompatibility. Asian Journal of Transfusion Science 2015; 9(2) 117-123
2) Mintz, P. D. (2011) Transfusion Therapy: Clinical Principles and Practice Bethesda, MD. AABB Press
3) Absence of anti-D alloimmunization in hematologic patients after D-incompatible platelet transfusions” J Cid, X Ortin, E Elies et al. Transfusion 2002
42(2): 173-176
4) Absence of D alloimmunization in D- pediatric oncology patients receiving D-incompatible single-donor platelets” R Molnar, R Johnson, LT
Sweat,TL Geiger. Transfusion 2002, 42(2):177-182
5) Low incidence of anti-D alloimmunization following D+ platelet transfusion: the anti-D alloimmunization after D-incompatible platelet transfusion
(ADAPT) study” J Cid, M Lozano, A Ziman et al. Br J Haematol 2015, 168(4):598-603.