The stubborn platelet - rEFRACTORINESS AT ITS WORST Dr. Anila Mathan, Consultant, Blood Bank & Hematology, SRM Institute of Medical Sciences , Chennai

Platelet transfusion refractoriness Clinically suspected when patients do not respond as expected to the transfusion Definition* :When 2 consecutive platelets transfusions lead to a 1 hour post transfusion Corrected Count Increment (CCI) of less that 5000 platelets per m2 per µl. Average expected increment 1 unit of random platelets 5000-10,000/cumm 1 unit of apheresis platelets 30,000-60,000/cumm If pre & post transfusion platelet counts are not appropriately tested the diagnosis is unlikely to be made It is after 2 tx as isolated poor responses to an individual plt tx is not uncommon *AABB 16th Edn

Guidelines for assessment of Platelet Refractoriness Pre transfusion count to be done just prior to transfusion. Post transfusion platelet count to be done1 hour & 18-24 hrs after transfusion to calculate Absolute Count Increment(ACI) or CCI. The clinical response of the patient to the transfusion by cessation of bleeding is an important indicator for further tests. Norms for our population are not yet established

Measure of Transfusion outcome Formula Values s/o refractoriness Absolute Count Increment (ACI) (Post transfusion plt count – Pre transfusion plt count) At 60 min ACI ,<5000/cumm after one unit of RDP Corrected Count Increment (CCI) (ACI x BSA m2)x1011 No. of plts transfused x 1011 At 10-60 min <5000/cumm Posttransfusion Platelet Recovery (PPR) ACI xTotal blood volume x100 No.of plts transfused At 60 min <30% At 24hrs <20% (Normal at 1 hr: 67%) AABB , Technical manual 16th Edn Pavenski et al, Tissue antigens 2012 BSA = Body surface area

PLATELET REFRACTORINESS Poor response to platelet transfusions Immune Causes (20%) Non Immune Causes (80%) Alloimmune Autoimmune Patient Related Platelet Related ABO incompatibility Fever , Sepsis Quality of platelets Pavenski et al, Tissue antigens 2012 HLA Class 1(80-90%) Splenomegaly Number of units Tx DIC Poor storage condition Human platelet antigen (10-20%) Active bleeds Dilution by blood volume HLA & HPA (rare) Drugs (Eg amphoterecin B

Platelet Antigens HLA ABH 8 weeks Class1 , IgG No dose response HPA Express a variety of antigenic markers on their surface,Some are shared : Blood group ABH , HLA,Some are specific : Platelet specific antigens Alloantibodies to mismatched HLA can develop and be detected within first 8 weeks of Transfusion Majority of clinically relevant HLA antibodies : IgG Directed against epitopes of HLA Class 1 (A & B) No dose response relationship HPA

Evaluation HLA Matching /Typing : Class 1 Screening for anti-HLA and anti-platelet antibodies Antibody-mediated or not? Solid-phase assay HLA antibody mediated or not? Panel reactive antibody (PRA) as general screen for HLA Ab positivity. (20-30%) Flow based assays :If positive, single antigen testing with microparticle beads to ID which antigen(s) to avoid in donors Luminex based single antigen bead assay C1q based SAB binding assay – better method for clinically relevant HLA abs (Fontaine etal,2011)

Used in Europe and US as an alternative to HLA matching Platelet crossmatching can used to check compatibility Platelet unit segment against patients serum Solid-phase red cell adherence (SPRCA) test most widely used method Disadvantage : Limited to units available for testing 5 day life to platelets, future transfusions will require re- crossmatching Used in Europe and US as an alternative to HLA matching Slichter SJ. Evidence-Based Platelet Transfusion Guidelines Hematology 2007

Prevention Non Immune Immune ABO compatibility Blood Bank role Clinicians role Immune ABO compatible HLA to ensure compatibility HPA ABO compatibility Ensure donor recipient ABO compatibility Rate of platelet refractoriness is 69% in ABO incompatible transfusions while in ABO compatible transfusion it is only 8%

Reduction of alloimmunisation Decrease in alloimmunisation from 45% to 17-21% in previously unexposed patients – LR & UVB irradiation (TRAP study , NEJM 1997) Universal prestorage leukoreduction incidence drop :Adopted in 19 countries Transfusion product Recipient IVIG, Cyclosporin Plasmapheresis Prophylactic single donor platelets Only HLA matched plts Leukoreduced platelets Irradiated platelets Canada 19%-7%, Europe ,US) Pavenski et al, Tissue antigens 2012

Management ABO matched platelet (<48 hrs old) HLA matching Challenge in obtaining a well matched donor HLA typed donor registry Identify HLA antibody specificities and select antigen compatible donors Degree of matching is important Cross reactive groups (CREGS) 2006 HLA matchmaker (software tool) - adequate CCI Recently 2010 epitope based matching PRA Platelet cross matching Whatever the methodology for matching Requires a large pool of dedicated typed donors No guarantee of a proper increment Not suitable for urgent requirements

Whatever the cause Cost of managing a refractory patient is very high (Meehan et al Am J Hematol 2000 ;64:251-6) How do we advice or manage a persistently refractory patient Small dose frequent platelet transfusion every 4-8 hrs This maintains vascular integrity even if the CCI does not increase IVIG Fibrinolytic inhibitors to stabilise any clots formed Recombinant factor VIIa to control bleeding Slichter SJ. Evidence-Based Platelet Transfusion Guidelines Hematology 2007

Indian scenario Pubmed showed that studies have been reported in 4 tertiary care centre The reports do not differ significantly from studies in the west. However this a condition which we need to keep in mind especially in patients requiring multiple transfusions. Shastry S, Chaudahary R,Clinical factors influencing corrected count increment. Trans Ap Sc, 2012, Marwarha N,Sharma RR, Consensus and controversies in platelet transfusion.Trans Ap sc2009 41(2) Bajpai etal. Platelet alloimmunization in multitransfused patients with haemato-oncological disorders,Trans Ap Sc2012, Pandey p etal 2012 A prospective quality evaluation of single donor platelets (SDP) - an experience of a tertiary healthcare center in India., Chodhry VP Platlet therapy ,IJP 2002 69(9)

Conclusion Always suspect refractoriness if patients symptoms or platelets counts don’t improve. Try to ensure ABO compatibility . Universal Leukodepletion seems to be one solution . Crossmatched compatible platelets seem to be another. Cost effectiveness of all approaches to this problem is a challenge.

Communication, Coordination,Logistics are the key to the success of any enterprise including tackling the stubborn platelet Thank you

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