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

2. 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 ,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

3. Guidelines for assessment of Platelet Refractoriness
Pre transfusion count to be done just prior to transfusion.
Post transfusion platelet count to be done1 hour & 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

4. 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 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

5. 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

6. 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

7. 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)

8. 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

9. 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%

10. 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

11. 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

12. 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

13. 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 sc (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 (9)

14. 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.

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

17. Selection