Upload
hilary-sanders
View
218
Download
0
Embed Size (px)
Citation preview
Tests of Hemostasis
Path 430/826
David LillicrapDepartment of Pathology and Molecular Medicine
Queen’s University, Kingston, Canada
Inherited Bleeding Disorders
Hemophilia A and B
von Willebrand disease
“Rare Bleeding Disorders”
Factor deficiencies: ie. FXI, FVII, FX
Platelet disorders: ie. Glanzmann’s Disease, Bernard-Soulier
Acquired Bleeding Disorders
• Liver dysfunction
• Vitamin K deficiency
• DIC: sepsis, cancer, obstetric pathologies
• Drugs: anticoagulants/anti-platelet agents
Clinical Evaluation of Bleeding
Excessive Mucocutaneous Bleeding
• Bruising
• Epistaxis
• Oral cavity bleeding
• GI/GU bleeding
• Menorrhagia
Musculoskeletal Bleeding
• Hemarthroses
• Soft Tissue/Muscle Bleeds
Prior Challenges to the Hemostatic System
• SurgeryTonsillectomy
• Dental ProceduresWisdom teeth extraction
1.Anecdotal bleeding histories
vs
2.Validated bleeding scores (bleeding assessment tools)
2005Vicenza0 to +340 min 2006
MCMDM-1VWD-1 to +440 min 2008
CondensedMCMDM-1VWD
-1 to +410 min 2009
PBQ-1 to +420 min
2010ISTH BAT
0 to +420 minRydz and James Nov 2012 JTH
Recent Evolution of Bleeding Assessment Tools
Type 1 Type 2 Type 30
10
20
30
Ble
edin
g S
core
(-1
to
+
4)p<0.001
p=0.173p<0.005
Previously Diagnosed with VWD (n=42)
ANOVA p<0.001
Utility of Bleeding Assessment Tools
1. Facilitate caregiver communication concerning severity of bleeding phenotype.
2. Justification for intensity of laboratory investigation.
Laboratory Tests of Hemostasis
Test Analyte
Platelet poor plasma
Routine Hemostasis Testing
Platelet poor plasma
Activator +Phospholipid
Thromboplastin
Ca2+ Ca2+
+ +
APTT PT
Initiation Phase
TFPI
Extrinsic Pathway Inhibition
TFPI
AmplificationPhase
**
*
Extrinsic Pathway
(prothrombin time - PT)
Intrinsic Pathway(aPTT)
Final Reaction
Thrombin Time
Limitations to Current Hemostasis Tests
• Insensitive to many bleeding pathologies
• No detection of hypercoagulability
• Standardization challenging
Mild hemophilia, VWD
Antithrombin, Protein C and S deficiency
Assessment of Platelet Contribution to Hemostasis
1. Platelet number
2. Platelet morphology
3. Platelet function
Aggregation studies with panel of agonsists
Light Transmission Platelet Aggregation Testing
Development of New “Global” Hemostasis Tests
• Enhanced sensitivity
• Reflection of complete hemostatic system
• More physiological
• But equally (if not more) difficult to standardize
Global Tests of Hemostasis
a) Thrombin generation assays (TGA)
a) Thromboelastography
IIa
ThrombinPro-coagulant
effects
Fibrinogen Fibrin
FVIII
FVIIIa
FV
FVa
FXIII FXIIIa TAFI TAFIa PAR1PAR4
FXI FXIa
TAT = thrombin – antithrombin complexes
Absent in Hemophilia
0
100
200
300
400
500
600
700
800
1 2 3 4 5 6 7 8 9 10 11 12 13
Subjects
Tot
al th
rom
bin
(nM
)Thrombin at 20 Minutes Over 6 Months
Brummel et al
Factor VIII FTGT on Normal Plasma: Dose Response
-500
0
500
1000
1500
2000
2500
3000
2 7 12 17 22 27 32 37 42 47 52 57 62
Time (min)
Fre
e T
hro
mb
in (
RF
U)
Normal Plasma (NP)
10% NP
1% NP
0.1% NP
0.01% NP
FVIII Deficient Plasma
Flourogenic Thrombin Generation Assay
Current detection limit
After –
•Confirmation of a clinical bleeding phenotype
•Extensive hemostasis laboratory investigation
30-40% of bleeding conditions are without a definitive diagnosis