Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
08.11.11
1
Überprüfung der Funktion von Thrombozyten in
Thrombozytenkonzentraten
2011
Simon Panzer Clinical Department for Blood Group Serology and
Transfusion Medicine, Medical University Vienna, Austria
platelet biology
Aggregation! GpIIb/IIIa! Fibrinogen! vWF!
Inflammation! PF4! beta-TG! IL-1! CD40-L! Rantes! Interferon-gamma!!
Adhesion! GPIb/V/IX! GPIIb/IIIa! GPIa, GPVI! Fibrinogen! vWF! P-Selectin!
Coagulation! Plasminogen! FV! FXI! Fibrinogen! Protein S! PAI-1! vWF!
Proliferation! PDGF! TGF-beta! EGF! ECGF! Interferon-gamma!
Vasoconstriktion! ADP/ATP! Thromboxan A2! Serotonin!
08.11.11
2
bewirken die primäre Hämostase!!Blutungsneigung tritt ein bei!
!- Verminderung der Anzahl!- Funktionsstörung!
!
Thrombozyten
platelet adhesion
platelet aggregation (expression of the fbg binding site)
platelet release (P-Selectin, ADP, TX2,...)
08.11.11
3
platelet -activation, -function
Alan Michelson 2005
determine activation – infer function
1. level of activation 2. “activatability“
measure function directly
08.11.11
4
testing for platelet function
• best: in vivo • under close to physiologic conditions:
- in the natural enviroment (red cells, leukocytes, plasma)
- under high shear
factors that activate platelets
ADP, thrombin, collagen, thromboxane A2,
epinephrine, HOCl-oxidised LDL,
immunglobulin complexes, complement system, secretion products of leukocytes, mast cells, bacteria
5-hydroxytryptamine (serotonin) mechanical stimuli
and others
many stimuli several different receptors
multiple signalling pathways
08.11.11
5
measure metabolism (aspirin) thromboxane as the end point serum thromboxane B2 urinary 11-dehydro thromboxane B2
agonist induced activation Platelet aggregometry (turbidimetric) Flow cytometry Platelet aggregometry (impedance) Plateletworks TEG PlateletMapping System Impact Cone and Plate(let) Analyser Impact-R
PFA-100
methods
Light transmission aggregometry (Born, O‘Brien) (LTA)
Assesses platelet activation by the reduction of turbidity of platelet rich plasma
requires the preparation of PRP and PPP
low standardisation
no physiologic environment, no shear
08.11.11
6
Yee, 2005
Variable response to epinephrine in healthy individuals
flow cytometry very little blood required many aspects of platelet function can be studied
not universally avaliable
skilled operator required
no shear
08.11.11
7
CD45
CD
45
platelet-leukocyte aggregates
CD45 CD45 CD45
CD45
CD
61
CD
61
CD
61
CD
61
Granulocytes
Monocytes
Lymphocytes
Platelets
w/o agonist
08.11.11
8
CD
61
CD
61
CD
61
CD
61
CD45 CD45 CD45
CD45
Granulocytes
Monocytes
Lymphocytes
Platelets
after activation
ASA 500 mg
i.v.
whole platelet aggregometry (impedance) the Multiplate® analyzer
08.11.11
9
firm adhesion and aggregation of platelets on the sensor surface enhances the electrical resistance between the 2 sensor wires
impedance aggregometry
Calatzis 2007
Plateletworks Based on platelet counting
before after addition of agonist
no shear
08.11.11
10
TEG PlateletMapping System
Thrombelastography The platelet part is abolished by GPIIb/IIIa antibodies and clot strength refelcts only fibrin formation. Thus, comparison without abciximab with that containing abciximab allows calculation of the platelet contribution to the clot formation.
no shear
citrated blood is passes through a small aperture in a collagen membrane
platelets adhere to the collagen surface and lead to a cessation of blood flow
parameter = Closure Time (CT)
2 cartridges: - EPI: costimulation by: shear stress,
collagen, epinephrin - ADP: costimulation by: shear stress,
collagen, ADP
PFA-100 ®
Shear rate 5000 - 6000-1
08.11.11
11
Impact-R
High shear 1800-1
08.11.11
12
platelets shall improve hemostasis
donor testing
testing the platelet concentrate
testing the transfused patient
donor testing
screenig by PFA-100 more specific:
aggregometry, flow cytometry,…….
08.11.11
13
frequent donations may impair donors’ platelet function
testing the platelet concentrate
various aspects can be tested, like differencies between apheresis methods effects of storage effects of manipulations…..
however, not all methods suit, as whole blood assays need reconstitution!
08.11.11
14
TRANSFUSION 2008
platelet P-selectin increases during storage, while induced P-selectin declines
platelet P-selectin, comparison of
apheresis devices CS 3000 plus
MCS 3p
Transfusion 1998
08.11.11
15
TRANSFUSION 2008
platelet adhesion and size of aggregates decline during storage
TRAP-6 induced multiple electrode aggregometry(MEA)
inducible aggregation differs between Amicus and Trima/MCS+
Transfusion 2009
08.11.11
16
TRAP-6 induced LTA
inducible aggregation differs between all 3 apheresis devices
Transfusion 2009
Testing function after transfusion: the recipient’s response
A whole blood method and testing under high shear is preferred However, all methods are restricted by the need of “near normal” platelet counts
08.11.11
17
improved in vivo platelet function after PC transfusion
platelet function was determined under high shear conditions by Impact-R: adhesion increased, while the size of aggregates did not change
Summary (but not last slide!)
Vox Sanguinis (2011) 101, 1–9
08.11.11
18
concluding remarks
There is a variety of laboratory tools to monitor platelet function.
There is a broad variation of their specificity and sensitivity. We currently have no single “universial“ method.
There is no “gold standard“ to determine a best method.