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ABO Compatibility and Platelet Transfusion

Guidelines for Selecting Blood Products

J. Lawrence Naiman, MD and Cherie S. Evans, MD
American Red Cross Blood Services - Northern California Region

Introduction

There is much confusion and uncertainty about the role of ABO compatibility in the selection of platelets for transfusion. In a perfect world, all patients would receive ABO-identical, or least ABO-compatible platelets. In the world we live however, this is not always possible. Frequently a decision must be made which product to use when our first choice is not available. To facilitate such decisions, it is necessary to understand the pros and cons of the various choices.

In this brief report we will review the roles of ABO-compatible vs ABO-identical transfusions, address concerns about adverse reactions and suboptimal responses to ABO-compatible platelets, and make recommendations on the roles of each product for patients with thrombocytopenia due to various causes.. These recommendations are based on a combination of our own experience, published literature and a consensus of opinions of a representative group of medical directors of Red Cross and non-Red Cross blood centers across the country.

Definitions of Platelet ABO Incompatibility and Compatibility

In the examples below, incompatibility implies an antibody in the recipient that could react against an antigen on the donor cells. The reverse situation, antibody in the donor plasma reacting with antigen on recipient cells is generally considered compatible, if the volume transfused is not excessive.

  Donor Red Cells Recipient Red Cells
Incompatible A B or O
  B A or O
  AB O
Compatible O A or B
Identical A A
  B B
  AB AB
  O O

Concerns About Adverse Reactions to ABO-compatible Platelets

  • Hemolysis of recipient red cells
  • Suboptimal response to platelets
  1. Hemolysis of recipient red cells

    Causes:

    1. Reaction between anti-A or anti-B in plasma of product vs recipient red cells

      (= plasma incompatibility)
      This is generally not a problem unless either:

      • the titer of anti-A or anti-B in the product is very high (rare), or
      • the volume of plasma infused is large in relation to the size of the recipient.

      Limiting the volume of incompatible plasma to 350 ml in an average-sized adult recipient (& proportionately less in a smaller patient or child, as illustrated in the accompanying table) is considered a safe alternative when ABO-compatible platelets are unavailable1. With this precaution, not only is hemolysis averted but levels of anti-A and anti-B in the recipient's serum are insufficient to cause problems in subsequent compatibility testing. Reports of hemolysis in recipients of ABOcompatible platelets are rare, occurring mainly in cases where the titer of anti-A or anti-B in the donor plasma was very high (usually much > 1:1000 by indirect antiglobulin test).

    2. Red cells of product vs recipient's plasma anti-A,B

      Most pheresis products today are clear and therefore this is not a problem. If the product is blood-tinged (therefore usually contains > 2 ml red cells), AABB Standards (I6.700; 18th ed.) require that a crossmatch must be performed with donor red cells against recipient serum.

  2. Suboptimal response to platelets
    1. ABO-compatible vs ABO-incompatible platelets

      Early studies have shown a reduced response (by approx. 25%) to ABOcompatible platelets (platelets of type A or B given to a recipient with anti-A or anti-B) compared to ABO-compatible platelets. This is attributed to either a very high titer of isohemagglutinin in the recipient, or a donor platelet with high expression of A or B. Petz2 recommends providing ABO-compatible platelets to patients with marrow failure requiring long-term platelet support. Where ABO-compatible platelets are not available, incompatible platelets are considered acceptable. However, if these patients experience poor rises from incompatible platelets, he recommends a trial of ABO-compatible platelets before resorting to HLA-compatible platelets.

    2. ABO-identical vs ABO-non-identical (but compatible) platelets

      Heal et al3, using historical controls, have shown that giving ABO-identical plateletpheresis products to patients with marrow failure requiring long-term platelet support produces better platelet rises in recipients than "ABO-compatible" platelets, and over the long-term there is a reduced cumulative usage of platelets. Studies by these same authors4 suggested this is due to platelet damage by circulating immune complexes formed between soluble A and B substance in the recipient's plasma and the transfused anti-A or anti-B.

      Although many blood centers try to provide ABO-identical platelets for this type of patient, most consider ABO-compatible platelets an acceptable alternative in times of shortage, or when the requirements for HLA or platelet crossmatch compatibility limit the number of available donors5. This is not an issue for patients whose platelet requirement is limited to one or two transfusion episodes, as in conjunction with surgery.

Recommendations:

  1. For patients with marrow failure requiring intensive short term or long-term platelet support

    ABO-identical platelets are the first choice. If not available and the need is urgent, there should be no hesitation in using ABO-compatible platelets.
  2. For all other (non-refractory) patients

    Offer ABO-compatible platelets when available. When not available ABO-incompatible platelets are acceptable, provided that:
    1. in the case of plasma incompatibility (e.g., O platelets to an A recipient) the above volume limitations are adhered to. When this requires entering the platelet bag to remove plasma this must be done within 6 hours of infusion.
    2. if the product is blood-tinged, a crossmatch of donor red cells vs patient serum is performed.
  3. For patients who appear refractory to platelets:

    Assuming that clinical causes of refractoriness (fever, infection, splenomegaly, etc.) appear unlikely, a trial of ABO-identical platelets should be given before resorting to HLA-matched or crossmatched products. For patients who are still refractory and need either of the latter products, the number of ABO-compatible donors may be limited. In this situation, especially when the need is urgent, ABOcompatible platelets are an acceptable and prudent option.

References

  1. Galel SB. Associate Medical Director, Stanford Medical School Blood Center. Personal communication. November, 1997.
  2. Petz LD.  Platelet Transfusions. pp 378 and 398. In Petz LD, Swisher SN, Kleinman S, Spence RK and Strauss RG (eds.). Clinical Practice of Transfusion Medicine. Churchill Livingstone Publications, New York. 3rd edition, 1996,.
  3. Heal JM, Rowe JM, McMican A, et al. The role of ABO matching in platelet transfusion. Eur J Haematol 1993; 50:110.
  4. Heal JM, Masel D, Rowe JM et al. Circulating immune complexes involving the ABO system after platelet transfusion. Br J Haematol 1993; 85:566.
  5. Naiman, JL. Personal survey of medical directors at selected ARC blood centers. Nov., 1997.

Adapted from Transfusion Services, Stanford Medical Center1.

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