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Transfusion medicine

Tranfusion side effects

Platelet refractoriness

Reviewer: Huy Phu Pham, M.D. (see Reviewers page)
Revised: 5 November 2011, last major update September 2011
Copyright: (c) 2007-2011, PathologyOutlines.com, Inc.

General
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● Platelet refractoriness is the inability to get an adequate increase in platelet count after transfusion (Arch Pathol Lab Med 2003;127:409, Haematologica 2005;90:247)
● Immune causes: anti-platelet or anti-HLA antibodies after multiple exposures from transfusion, pregnancy or transplantation (Transfusion 2005;45:761)
       ● Usually occur within 21-28 days after primary exposure (pregnancy or transfusion) or 4 days after reexposure
       ● Anti-HLA antibodies causes 30-40% of platelet refractoriness
● Non-immune causes: usually due to platelet consumption
       ● Fever, infection, drugs, bleeding, hypersplenism, DIC
● Usually 4-6 units of platelets or 1 unit of apheresis platelets raises platelet count by 50-100K/μL; if no rise in platelet count after 1 hour, cause is likely immune-mediated
● If platelet count increases after 1 hour but drops after 24 hours, cause is likely consumption

Evaluation of platelet refractoriness
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● Determine if cause is immune- or non-immune-mediated
● Do at least 2 one hour post-transfusion platelet counts on consecutive days
● Calculate the 1-hour CCI (body surface area x platelet count increment x 10¹¹)/(number platelets transfused)
● Platelet refractoriness is two one-hour CCI of <5000 on consecutive days
● If immune-mediated, send for anti-HLA and anti-HPA antibody testing

Treatment
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● Initial step: give ABO identical platelets stored <48 hours
● ABO identical platelets and platelets from first degree relatives are helpful unless relatives may be source for stem cell transplantation
● Determine anti-HLA and anti-HPA antibody
● Select HLA-matched or crossmatched platelets for transfusion to avoid crossreactive HLA or platelet antigens
● IVIG may have short term benefit
● Giving larger doses of platelets is usually not helpful if patient is bleeding (Blood 2005;105:4106)
● Other potential therapies: immunosupression, rituximab, IVIG, plasma exchange, antifibrinolytic agents, recombinant factor VIIa

Prevention
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● Reduce leukocyte content of platelet components (Blood 1991;77:201, Blood 2004;103:333)
● Prescreening for antibodies (Transfus Apher Sci 2005;33:157)

Differential diagnosis
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● Neonatal alloimmune thrombocytopenia (due to maternal antibodies, Transfusion 2007;47:901)

End of Transfusion Medicine > Tranfusion side effects > Platelet refractoriness

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