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HEM Exam 1 > Hemostasis Assays > Flashcards

Hemostasis Assays Flashcards

1
Q

how is blood kept from clotting during a coagulation screening test?

A
  • remove calcium using citrate
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2
Q

general activating agents for tests of coagulation

A
  • calcium

- phospholipid

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3
Q

routine coagulation tests

A
  • prothrombin time (PT)
  • activated partial thromboplastin time (aPTT)
  • thrombin time (TT) or thrombin clotting time (TCT)
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4
Q

TCT tests for

A
  • conversion of fibrinogen to fibrin

- using thrombin

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5
Q

activating agents for thrombin time

A
  • we do not use activating agents
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6
Q

how to do a TT test

A
  • citrated plasma
  • add thrombin
  • record the time until clot forms
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7
Q

what causes a prolonged TT

A
  • low fibrinogen
  • abnormal fibrinogen
  • inhibitor of added thrombin
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8
Q

another name for low fibrinogen

A
  • hypofibrinogenemia
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9
Q

another name for abnormal fibrinogen

A
  • dysfibrinogenemia
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10
Q

ways to get abnormal fibrinogen

A
  • inherited

- acquired

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11
Q

acquired abnormal fibrinogen from

A
  • severe liver disease
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12
Q

ways to get inhibitor of added thrombin

A
  • direct inhibitor

- indirect inhibitor

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13
Q

direct inhibitor example

A
  • argatroban

- dabigatran

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14
Q

indirect inhibitor example

A
  • heparin
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15
Q

how to do the prothrombin time

A
  • citrated plasma
  • add thromboplastin and calcium
  • record the time until clot forms
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16
Q

thromboplastin provides which compounds

A
  • tissue factor

- phospholipid

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17
Q

prothrombin time measures which part of the coagulation cascade

A
  • extrinsic pathway
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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
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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
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20
Q

sensitivity of PT compared to TT

A
  • PT much less sensitive than TT
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21
Q

what things is the PT much less sensitive to

A
  • heparin
  • abnormal fibrinogen
  • FDPs
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22
Q

the common pathway factors

A
  • 10
  • 5
  • 2 (prothrombin)
  • fibrinogen
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23
Q

how do we get low levels of factor 7?

A
  • congenital

- acquired

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24
Q

acquired ways to get low levels of factor 7

A
  • deficiency of vitamin K
  • vitamin K inhibitors
  • DIC
  • liver disease
25
Q

vitamin K dependent factors

A
  • 2
  • 7
  • 9
  • 10
  • protein C
  • protein S
26
Q

how do vitamin K factors get into the plasma membrane

A
  • inserted via their gamma carboxyl groups
27
Q

purpose of vitamin K

A
  • source of the gamma carboxyl group
28
Q

sources of vitamin K

A
  • diet

- gut flora

29
Q

diet sources of vitamin K

A
  • green leafy vegetables
30
Q

causes of vitamin K deficiency

A
  • dietary
  • antibiotics
  • fat malabsorption
  • being a newborn
31
Q

how to calculate the INR

A

mean normal PT

32
Q

ISI

A
  • given on the box for a new batch of thromboplastin
33
Q

normal value for INR

A
  • 1
34
Q

aPTT measures which part of the coagulation pathway?

A
  • the intrinsic pathway
35
Q

how to perform the aPTT

A
  • add activator
  • add partial thromboplastin and calcium
  • record the time until clot forms
36
Q

what does the activator in the aPTT do?

A
  • provides negative charges to activate the contact system
37
Q

components of the contact system

A
  • HMWK
  • PK
  • factor 12
38
Q

what is missing in partial thromboplastin that is in complete thromboplastin

A
  • tissue factor is missing
39
Q

does partial thromboplastin have phospholipid

A
  • yes!
40
Q

what causes a prolonged aPTT?

A
  • 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
Q

factors in the common pathway affecting prolonged aPTT

A
  • factor 2
  • factor 5
  • factor 10
  • fibrinogen
42
Q

contact factors affecting prolonged PTT

A
  • factor 12
  • HMWK
  • PK
43
Q

hemophilia factors affecting prolonged PTT

A
  • factor 11 - hemo C
  • factor 9 - hemo B
  • factor 8 - hemo A
44
Q

warfarin in excess or severe vitamin K deficiency due to their effects on

A
  • 9
  • 10
  • 2
45
Q

another name for lupus inhibitor

A
  • lupus anticoagulant
46
Q

what is a lupus inhibitor

A
  • an autoantibody directed against phospholipid
47
Q

how to tell if it’s a lupus inhibitor

A
  • antibody prolongs coagulation reactions in test tube

- prolongation blocked by additional of more phospholipid in the reaction mix

48
Q

broad differential of prolonged aPTT

A
  • factor deficiency

- inhibitor

49
Q

how a mixing study works

A
  • take patient’s plasma
  • mix it 1:1 with normal plasma
  • repeat aPTT
50
Q

if the clotting times remain prolonged, the result of the prolonged PTT is the

A
  • inhibitor
51
Q

if the clotting times normalize, the result of the prolonged PTT is the

A
  • factor deficiency

- must be within normal range. cannot decrease and call it good

52
Q

Ddx if both PT and PTT are prolonged

A
  • deficiency of common pathway factor
  • excess of warfarin
  • excess of heparin
  • multiple factor deficiencies

CWH MF

come hang with me, fucker!

53
Q

multiple factor deficiencies due to

A
  • severe liver disease

- severe DIC

54
Q

tests of primary hemostasis

A
  • bleeding time

- PFA 100

55
Q

how PFA 100 works

A
  • whole blood sucked through

- platelets plug up collagen coated grid

56
Q

closure time in PFA 100

A
  • how long it takes for flow to stop
57
Q

what makes PFA-100 prolonged

A
  • low platelet count
  • low hemoglobin
  • low vWF
  • abnormal platelet function
58
Q

low platelet numbers

A

< 100 x 10^9

59
Q

low hemoglobin numbers

A

< 10 g/dL

HEM Exam 1 (22 decks)

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