2. Platelets
Platelets are anucleated
blood cells
They arise from bone
marrow megakaryocytes
They play key role in
blood hemostasis
Normal blood platelet
count is 140-450x1000/uL
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4. Thrombasthenia
Hereditary as Glanzmann thrombasthenia,
Bernard-Soulier Syndrome,…… etc
Acquired thrombasthenia as in drug
induced cases due to salicylates and non-
steroidal anti-inflammatory drugs
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5. Indications of Platelet Transfusion
Severe thrombocytopenia <5000/ul in
patients without clinical bleeding
Thrombocytopenia with clinical bleeding or
as supportive therapy during
chemo/radiotherapy and in
transplantations
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6. Contraindications of Platelet
Transfusion
Autoimmune thrombocytopenia
Thrombotic Thrombocytopenic Purpura &
related syndromes
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7. Platelet Donor Criteria
Age, 18 – 55 years
Sex
Donor Screening
Blood Screening (HBV, HCV, HIV 1&2
serology & ID-NAT + Syphilis Ab)
Blood group & Rh
No Salicylates or non steroidal anti-
inflammatory drugs for 7 days
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8. Preparation of Platelet Concentrates From
Donated Blood Units
Platelets can be prepared from freshly donated blood
units by deferential centrifugation in cooling centrifuges
Prepared units can be stored for 1,3 or 5 days at 22° C
depending on method of preparation
Platelet content/concentrate = 0.5x10¹¹ platelets in a
volume of 40-50 ml
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9. Preparation of Platelet Concentrate
Using Cell Separators
Blood donors can donate platelets only by cell
separators
Depending on donor platelet count one can obtain single
or double platelet therapeutic dose
Platelet therapeutic dose= 3x10¹¹ in 200 ml plasma
volume and can be stored for 1,3 or 5 days at 22° C on
platelet shaker
Ideally it should contain <5x10*6 leucocytes
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10. Dose of Platelet Transfusion
In clinical bleeding, platelet transfusion
should be given untill bleeding is controled
In prophylaxis as in surgery and
chemo/radiotherapy, the required level of
platelets is determined by the clinician
according to many factors, eg. Type of
surgery, clinical condition of the patient,
……. etc
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11. Dose Response
Cessation of clinical bleeding
Corrected Count Increment (CCI)
– CCI at 1 hr = (Platelet Countpost- platelet countpre)-BSA
No. of units transfused/No. of platelets transfused
– CCI at 1 hr = >4000-5000/ >7000-10000
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14. Platelet Immunology
Platelets express HLA class I antigens,
ABH, P, Lewis and I
5 biallelic platelet specific antigen systems
Each system includes a high frequency
antigen >96% and a low frequency
antigen
Some may be detected on other cells
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15. Allo-Antigens in Platelet Glycoproteins
Allo-Antigen Synonym Caucasian Japanese GP Location
HPA-1a Zw a, PIA1 97.9 99.9 IIIa
HPA-1b Zw b, PIA2 26.5 3.7
HPA-2a Kob 99.3 NT Ib
HPA-2b Koa, Siba 14.6 25.4
HPA-3a Baka, Leka 87.7 78.9 IIb
HPA-3b Bakb 64.1 NT
HPA-4a Pena, Yukb 99.9 99.9 IIIa
HPA-4b Penb, Yuka 0.2 1.7
HPA-5a Brb, Zavb 99.2 NT Ia
HPA-5b Br , Zav , Hc 20.6
a a a
NT
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16. Platelet Glycoproteins
HPA5 HPA1
HPA2 HPA3
s
s
ss
β α
β2M HLA gpIb gpIX gpV gpIaIIa gpIIbIIIa
In NAITP Platelet Allo-Antibodies are directed against
HPA1a 78%
HPA5b 17%
HPA3a 3%
others 2%
Data from Mueller-Eckhardt et al. 1989
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17. Platelet Antibodies
A platelet reactive antibody may react against
any antigen on the platelet
Platelet antibodies may be HLA (class I) ,
platelet specific antigen, ABH, ... Etc specific
antibodies
Like red cell antibodies, they are IgG or Ig M and
cause mostly extravascular destruction
The antibodies may be auto or allo-antibodies
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18. Post Transfusion Purpura, PTP
• PTP is a rare (1 / 50000) but severe side effect of blood transfusion
that resembles DTR due to red cell transfusion
• In more than 90% of patients PTP is encountered in women who are
HPA1b and have developed anti HPA1a antibodies due to
immunization by previous pregnancy
• Fall in platelet count 5 to 10 days after transfusion of any of the blood
components
• Mortality is high, some 5% of PTP cases die
• The most effective therapy is plasmapheresis &/or IVIg
• Corticosteroids is an essential therapy in combination with other
therapies
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19. Graft Versus Host Disease (GVHD)
It is reactivity of donor lymphocytes
against host tissues in immuno-
suppressed patients
This causes dermatitis, hepatitis,
gastroentritis & if it happens due to
transfusion of cellular blood components it
is usually fatal
It can be prevented by irradiation of RBCs
& platelets
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20. Platelet Refractoriness, PR
• Platelets are given to thrombocytopenic cancer patients to prevent
major hemorrhage
• PR is the less than expected increase in platelet count
• PR occurs in 10 to 20% of patients who receive prophylactic platelets
• 1.4 million platelet concentrates from 5.6 million donations are used
each year in the EU
• Anti-HLA or anti-HPA antibodies destroy transfused random
ABO/RhD-compatible platelets
• The refractory state increases the chance of major bleeding,
including cerebral bleeding
• Treatment of choice is HLA and HPA selected donor platelets or
platelet cross matching
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21. Causes of Platelet Refractoriness
Non-immunological
– Splenomegaly
– Drugs (eg amphotricin B)
– Accelerated platelet consumption
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23. Leuco-Reduced Cellular Components
QC using
flowcytometry
Staining of nucleated
cells with propodium
iodide, PI
Simple equation to
obtain residual
leucocytes in a
concentrate
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25. Platelet Cross Matching Experience
6 cases of
immunological
refractoriness
On average 1/9
cross-matched
donors was found
comp.
Delivery time 1 – 2
days
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26. Risks Still Exist
in Blood Transfusions
1. Bacteria
Introduced during
collection
5. Leukocytes 2. Emerging/Unknown
Adverse immune responses
and transfusion reactions Viruses
4. Known Pathogens 3. Window Period
For which no assay Limits of detection of
is available current assays
(e.g. false negatives)
Transfusion Recipient
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27. Bacterial Contamination
Risk of bacterial contamination in platelet doses can be
as high as 1:2,0001
The mortality rate for platelet-related sepsis is one in four 2
A prospective study3 of 3,584 platelet transfusions in 161
bone marrow transplant patients demonstrated risk of
symptomatic bacteremia as:
• 1 per 16 patients
• 1 per 350 transfusions
• 1 per 2,100 platelet units
UK SHOT data reported three deaths in UK between
1996 and 1999 as a result of bacterial contamination4
1
Blajchman MA, The Safety of the Blood Supply, Hillyer CD ed. 1999: 18-27. 3
Chiu EKW et al, Transfusion. 1994:34:950-953.
2
Goodnough LT et al, New England Journal of Medicine. 1999; 340/6: 438-447. 4 Love EM et al. The Serious Hazards of Transfusion Annual
Report 1999-2000. Published March 2001.
28. Emerging/Unknown Pathogens
It is impossible to know if and when emerging
pathogens will threaten the safety of the blood
supply
Impact of previously unknown pathogens is
demonstrated through HCV and HIV
New viruses continue to emerge at a rate of every
2–3 years with a potentially damaging virus
transmitted through blood every 5 years1
1
LEK Consulting. Market research commissioned by Baxter Healthcare Corporation.
Boston, MA, USA: January 2001.
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29. Window Period (False Negative)
NAT/PCR testing has significantly reduced the
window period but it still exists
Collection of blood during the window period is likely
the most important source of residual HIV infections1
Median Time to NAT/PCR2
Virus Test Seroconversion Positive
HIV p-24 antigen 16 days 11 days
anti-HIV 22 days
HCV anti-HCV 70 days 12 days
HBV HBsAg 56 days 40 days
1
Dodd RY, The Safety of the Blood Supply, ed. Hillyer CD. 1999: 1-17.
2
Bush MP, Kleinmann SH, Transfusion. 2000; 40: 143-159.
30. Current Risk of Transfusion
Transmitted Virus
Risk per Unit Transfused (post-NAT)
Virus USA France Germany
HIV 1:1,576,000 1:1,000,000 1:1,900,000
HCV 1:223,000 1:200,000 1:<350,000
HBV 1:135,000 1:180,000 1:220,000
Cumulative 1:79,808 1:86,505 1:126,121
Risk
Stramer SL, Current Opinion in Hematology. 2000; 7: 387-391.
Pillonel J et al, Eurosurveillance. 1998; 3: 76-79.
Seifried E et al, British Journal of Haematology. 2000; 109: 694-698.
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31. Known Pathogens
Transmission There are pathogens that are known,
but not routinely screened for
of parasites by transfusion, although currently rare in
developed countries, does occur
Donor demographics may bring change in risk level
of transfusion-transmitted agents
Example: Incidence of malaria and Chagas’ disease seems
to be increasing
• Travel to endemic areas increasing
• Climate changes
• Immigration
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32. Pathogens Known to be Transmitted
by Blood Transfusion
Routinely Screened
Family Pathogen Disease Yes No
Hepatitis viruses HBV, HCV Hepatitis X
HEV, HGV Hepatitis X
Retroviruses HIV-1 & -2 AIDS X
HTLV-I & -II Malignant lymphoproliferative X
disorders, neuropathy
Herpes viruses CMV CMV retinitis, hepatitis,
pneumonia X
EBV Epstein-Barr Syndrome X
HHV-8 Kaposi’s Sarcoma X
Parvoviruses B19 Aplastic anemia X
Bacteria Gram-negative, Gram-positive Sepsis X
Treponema pallidum Syphilis X
Borrelia burgdorferi Lyme disease X
Rickettsia rickettsii Rocky Mountain Spotted Fever X
Ehrlichia chafeensis Ehrlichiosis X
Parasites Trypanosoma cruzi Chagas’ disease X
Babesia microti Babesiosis X
Leishmania donovani Leishmaniasis X
25/12/2003 Plasmodium spp. Shabrawishi BTC
Malaria X
Based on US practices
34. Nucleic Acids Must “UnZip”
During Pathogen Replication
Replication of
DNA / Strand Separation
Nucleic Acids
RNA
and Pathogen
25/12/2003 Shabrawishi BTC
35. Amotosalen
Mechanism of Action
Amotosale UVA Illumination
n
DNA or
RNA
of
pathogen Docking Permanent
Crosslinking
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36. Psoralen Locks Nucleic Acid
and Prevents Replication
DNA / RNA No Strand Separation No Replication of
Nucleic Acids or Pathogens
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37. Psoralen Permanently Crosslinks Both Single-
and Double-Stranded Nucleic Acids
Helical
Regions
Single-stranded
DNA or RNA
Double-stranded
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DNA or RNA
38. INTERCEPT Blood System:
The Only System in Clinical Trials for All
Three Blood Components
Platelets
Plasma
No RBCs
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39. INTERCEPT Blood System: Status
Preclinical Phase I Phase II Phase III Regulat Clinical
ory use
Review
INTERCEPT Platelets -
EU
INTERCEPT Platelets -
US
INTERCEPT Plasma
Stopped
INTERCEPT Red Cells*
*Phase I data allowed us to move directly to Phase III
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40. Psoralen Blood System for Platelets and
Plasma Use a Similar Process
The Psoralen Blood System for platelets
and plasma use the same compound
This compound, amotosalen, is activated
by UVA light
Both systems use the same UVA device
(the Illuminator)
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41. Conclusion
Platelet transfusion is an important
therapeutic modality in transfusion
medicine
GMP, proper prescription and accurate
monitoring are all essential factors for safe
and effective outcome
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