Hemostasis Assays Flashcards
1
Q
how is blood kept from clotting during a coagulation screening test?
A
- remove calcium using citrate
2
Q
general activating agents for tests of coagulation
A
- calcium
- phospholipid
3
Q
routine coagulation tests
A
- prothrombin time (PT)
- activated partial thromboplastin time (aPTT)
- thrombin time (TT) or thrombin clotting time (TCT)
4
Q
TCT tests for
A
- conversion of fibrinogen to fibrin
- using thrombin
5
Q
activating agents for thrombin time
A
- we do not use activating agents
6
Q
how to do a TT test
A
- citrated plasma
- add thrombin
- record the time until clot forms
7
Q
what causes a prolonged TT
A
- low fibrinogen
- abnormal fibrinogen
- inhibitor of added thrombin
8
Q
another name for low fibrinogen
A
- hypofibrinogenemia
9
Q
another name for abnormal fibrinogen
A
- dysfibrinogenemia
10
Q
ways to get abnormal fibrinogen
A
- inherited
- acquired
11
Q
acquired abnormal fibrinogen from
A
- severe liver disease
12
Q
ways to get inhibitor of added thrombin
A
- direct inhibitor
- indirect inhibitor
13
Q
direct inhibitor example
A
- argatroban
- dabigatran
14
Q
indirect inhibitor example
A
- heparin
15
Q
how to do the prothrombin time
A
- citrated plasma
- add thromboplastin and calcium
- record the time until clot forms
16
Q
thromboplastin provides which compounds
A
- tissue factor
- phospholipid
17
Q
prothrombin time measures which part of the coagulation cascade
A
- extrinsic pathway
18
Q
if TF/VIIa can also activate factor 9, how come the PT is not sensitive to factor8/9 deficiency?
A
- the TF in vast excess drives the pathway toward X activation only
19
Q
what causes a prolonged PT
A
- anything that prolongs the TT
- anything that lowers levels or inhibits common pathway factors
- low levels of Factor 7
20
Q
sensitivity of PT compared to TT
A
- PT much less sensitive than TT
21
Q
what things is the PT much less sensitive to
A
- heparin
- abnormal fibrinogen
- FDPs
22
Q
the common pathway factors
A
- 10
- 5
- 2 (prothrombin)
- fibrinogen
23
Q
how do we get low levels of factor 7?
A
- congenital
- acquired
24
Q
acquired ways to get low levels of factor 7
A
- deficiency of vitamin K
- vitamin K inhibitors
- DIC
- liver disease
25
vitamin K dependent factors
- 2
- 7
- 9
- 10
- protein C
- protein S
26
how do vitamin K factors get into the plasma membrane
- inserted via their gamma carboxyl groups
27
purpose of vitamin K
- source of the gamma carboxyl group
28
sources of vitamin K
- diet
| - gut flora
29
diet sources of vitamin K
- green leafy vegetables
30
causes of vitamin K deficiency
- dietary
- antibiotics
- fat malabsorption
- being a newborn
31
how to calculate the INR
patient's PT ^ ISI
-----------------
mean normal PT
32
ISI
- given on the box for a new batch of thromboplastin
33
normal value for INR
- 1
34
aPTT measures which part of the coagulation pathway?
- the intrinsic pathway
35
how to perform the aPTT
- add activator
- add partial thromboplastin and calcium
- record the time until clot forms
36
what does the activator in the aPTT do?
- provides negative charges to activate the contact system
37
components of the contact system
- HMWK
- PK
- factor 12
38
what is missing in partial thromboplastin that is in complete thromboplastin
- tissue factor is missing
39
does partial thromboplastin have phospholipid
- yes!
40
what causes a prolonged aPTT?
- problems with common pathway factors
- problems with contact factors
- problems with hemophilia factors
- warfarin in excess
- severe vitamin K deficiency
- unfractionated heparan
- lupus inhibitor
CCHLWKH
Could Coagulation Have Less
Work? Hello, K!
41
factors in the common pathway affecting prolonged aPTT
- factor 2
- factor 5
- factor 10
- fibrinogen
42
contact factors affecting prolonged PTT
- factor 12
- HMWK
- PK
43
hemophilia factors affecting prolonged PTT
- factor 11 - hemo C
- factor 9 - hemo B
- factor 8 - hemo A
44
warfarin in excess or severe vitamin K deficiency due to their effects on
- 9
- 10
- 2
45
another name for lupus inhibitor
- lupus anticoagulant
46
what is a lupus inhibitor
- an autoantibody directed against phospholipid
47
how to tell if it's a lupus inhibitor
- antibody prolongs coagulation reactions in test tube
| - prolongation blocked by additional of more phospholipid in the reaction mix
48
broad differential of prolonged aPTT
- factor deficiency
| - inhibitor
49
how a mixing study works
- take patient's plasma
- mix it 1:1 with normal plasma
- repeat aPTT
50
if the clotting times remain prolonged, the result of the prolonged PTT is the
- inhibitor
51
if the clotting times normalize, the result of the prolonged PTT is the
- factor deficiency
| - must be within normal range. cannot decrease and call it good
52
Ddx if both PT and PTT are prolonged
- deficiency of common pathway factor
- excess of warfarin
- excess of heparin
- multiple factor deficiencies
CWH MF
come hang with me, fucker!
53
multiple factor deficiencies due to
- severe liver disease
| - severe DIC
54
tests of primary hemostasis
- bleeding time
| - PFA 100
55
how PFA 100 works
- whole blood sucked through
| - platelets plug up collagen coated grid
56
closure time in PFA 100
- how long it takes for flow to stop
57
what makes PFA-100 prolonged
- low platelet count
- low hemoglobin
- low vWF
- abnormal platelet function
58
low platelet numbers
< 100 x 10^9
59
low hemoglobin numbers
< 10 g/dL
