coagulation in a blood vessel: introduction to coagulation ... · low titer or slow acting antibody...
TRANSCRIPT
1
Introduction to coagulation and laboratory tests
Marc Jacquemin
Special Haemostasis Laboratory
Center for Molecular and Vascular Biology University of Leuven
Coagulation in a blood vessel: fibrin stabilises the hemostatic clot
Platelet immunostaining Fibrin staining
Polymerisation of fibrin stabilises the hemostatic clot = secondary hemostasis
Norledge BV, et al. Proteins. 2003;53:640-8
Expression of Tissue Factor (TF) and Factor VIIa on phospholipid surfaces in damaged tissues
Va V
IXa IX
XIa XI
X Xa
VIIIa VIII
VIIa/TF
Initiation of coagulation
Prothrombin Thrombin
Amplification Fibrinogen Fibrin
Sustained hemostasis
FXIII
FVIII is bound to vWF in plasma
A1
FVIII
vWF
2
*
Factor VIIIa Factor IXa
Phospholipids
* A3!
A2!
A1!
C2!
* *
X 100.000 by Factor VIII
Factor X
Factor Xa
Haemostasis
Activated Factor VIII as cofactor of Factor IXa
*
Hydrophobic residues
Basic residues Phospholipid binding site
Pratt et al., Nature 2000
FV and FVIII binding to phospholipids
d Ca ++
Gla Gla
Val Leu
Phe
hydrophobic
basic
Phospholipids
Gla: γ carboxy glutamic acid
FVII, FIX, FX, FII binding to phospholipids:
Gla domain
Glutamic acid oxidized vitamin K
reduced vitamin K
vitamin K
-OOC γ-carboxy glutamic acid
Cγ CH2
COO-
H Cγ CH2
COO-
γ-carboxylase
protein
VKOR
VKR
vitamin K cycle
anti-vit K
CH2
CH2
Coagulation and phospholipids Anti-phospholipid antibodies
Thrombosis
but no bleedings
3
Coagulation assays
X Xa
VIIa
Prothrombin Thrombin
Fibrinogen Fibrin
Prothrombin time (PT) + TF + phospholipids + Ca++
time between the addition of reagents to citrate plasma and detection of a clot.
PT results
• time (seconds)
• percent (%) by comparison to PT with dilutions of plasma 13 sec = 100% 40 sec = 10%
• International Normalized Ratio (INR) 13 sec = 1 40 sec = 3.5
Follow up of Anti-vit K treatment Va V
IXa IX
XIa XI
X Xa
VIIIa VIII
Prothrombin Thrombin
Fibrinogen Fibrin
APTT (Activated Partial Thromboplastin Time)
XIIa XII
HK / PK Contact Activation pathway
+ phospholipids + Ca++
+ non physiological surface (glass, silica, kaolin)
Interpretation of coagulations assays
Va V
IXa IX
XIa XI
X Xa
VIIIa VIII
Prothrombin Thrombin (IIa)
Fibrinogen Fibrin
APTT nl XIIa XII
HMWK / PK
X Xa
VIIa
Prothrombin Thrombin (IIa)
Fibrinogen Fibrin
PT >
Prolonged isolated PT
4
Isolated prolonged PT (lower % value, increased INR)
acquired decreased FVII
• early liver disease • early anti-vit K treatment
« anti-phospholipid » antibody *
constitutive FVII defect
not bleeding disorders *
Va V
IXa IX
XIa XI
X Xa
VIIIa VIII
Prothrombin Thrombin (IIa)
Fibrinogen Fibrin
APTT > XIIa XII
HMWK / PK
X Xa
VIIa
Prothrombin Thrombin (IIa)
Fibrinogen Fibrin
PT nl
Prolonged isolated APTT
Isolated prolonged APTT
acquired • inhibitor antibody (FVIII) • « anti-phospholipid » antibody
constitutive • Von Willebrand disease • hemophilia A and B (FVIII, FIX) • FXI • FXII (contact activation pathway)
not bleeding disorders *
*
*
FVIII vWF
Differential diagnosis of isolated prolonged APTT
mix of patient’s plasma with normal plasma
NO correction of the APTT:
ANTIBODY
inhibitor antibody? anti-phospholipid antibody?
Correction of the APTT:
DECREASED FACTOR low titer or slow acting antibody
Factors?
Prolonged PT and APTT
Va V
IXa IX
XIa XI
X Xa
VIIIa VIII
Prothrombin Thrombin (IIa)
Fibrinogen Fibrin
APTT
XIIa XII
HMWK / K
X Xa
VIIa
Prothrombin Thrombin (IIa)
Fibrinogen Fibrin
PT
5
Acquired prolonged aPTT and PT
Clinical state Deficiency • advanced liver disease VII, V, IX, X , II • vit K deficiency VII, IX, X, II
• acute DIC V • massive blood transfusion V
• lupus inhibitor none after dilution • antibody to FV V
• rare systemic diseases Gaucher’s disease V, X
Nieman Pick disease Amyloid
• heparin • oral anticoag treatment VII, IX, X, II