Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Haematology and Transfusion Science > Lab Investigations In Haemostasis > Flashcards

Lab Investigations In Haemostasis Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

What factor are haemophilia A patients deficient in?

A

VIII

8

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the 5 main lab tests done to examine deficiencies or defects in the coagulation factors?

A

PT (prothrombin time)
APTT (activated partial thromboplastin time)
Fibrinogen
TT (thrombin time) + platelet counts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What tests are not usually done on patients unless they are going to theatre (generally)?

A

Vascular and platelet.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the principle of PT?

A
  • measures clotting time of plasma
  • in presence of optimal conc of tissues extracted such as thromboplastin and calcium.
  • indicated the efficiency of the extrinsic clotting system.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Which clotting system does the PT test interrogate?

A

The integrity of the extrinsic clotting system.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Which factors does thromboplastin bind to ? What is the the extrinsic pathway

A

7, 5, 10, 2 and 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What was the PT originally thought to measure?

A

Prothrombin (II)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What does PT test now known to depend on ? Pathway wise

A

V, VII, X and fibrinogen concentration in plasma.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is a monitoring function of the PT test?

A

To monitor for Warfarin - this interferes with Vitamin K dependent factors.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the vitamin K dependent factors?

A

II, VII, IX and X

PROTEIN C AND S

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Which coagulation factors does warfarin lower the level of activtity?

A

2, 7, 9 and 10 and their one stage.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why is warfarin prescribed to some patients?

A

To thin blood - less likely to clot.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What can happen if a patient experiences an overdose on warfarin ?

A

This knocks out all of their coagulation factors - about 1 % of those on warfarin have these bleeding episodes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the concentration of trisodium citrate in a patient blood sample in prep for PT test?

A

32g/L (9:1)

It is then centrifuged

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is added to the patients platelet poor plasma (100ul) in PTT?

A

Thromboplastin and calcium chloride (200ul)

All mixed at 37 C and time of clot is measured.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the instrument used to measure the clot of the patient after a PT test?

A

Coagulometer.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the reference range for the PT test and what do these values depend on?

A

9-13 seconds, depending on the thromboplastin used.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does different thromboplastin do to the quality of the assay?

A

It can vary its sensitivity - all have an ISI value.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is ISI and what is the necessary value for an accurate PT test?

A

International sensitivity Index, as close to 1 as possible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Are PT tests done in singles or doubles?

A

Done in singles and are reported accordingly.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Where was thromboplastin historically collected?

A

From tissues rish in thromboplastin such as the brain and the placenta.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What does the conversion of MPTP to MPP+ do in the mechanism of Parkinson’s disease?

A

Inhibits the mitochondrial Complex I - specifically in dopamine neurons in the S.Nigra region of the brain when these motor controlling neurons degenerate - PD develops quickly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What can a PT test be used to calculate?

A

INR value, using the mean normal prothrombin time and the ISI of a thromboplastin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is ISI?

A

This is the international sensitivity index. WHO sets = should equal 1.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the purpose of ISI?

A

Tre regulate INR and PT values, taking into account different analysers etc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is INR?

A

This is the ratio of a patients PT to the mean PT to the power of the ISI value.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What does a high INR mean?

A

Blood is over coagulated, patient may bleed - dose of warfarin needed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the therapeutic range for patients on warfarin?

A

1.8 - 3
1.8 - risk of thrombotic event, 3 - run the risk of bleeding.
Low = increase warfarin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What are the 4 reasons why a patients INR would be high/prolonged?

A
  • Vitamin K 2, 7, 9 or 10
  • Liver disease
  • Hereditary factor deficiency in factor 7
  • Warfarin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Thromboplastin was originated from?

A

Tissue extracts obtained from different species and different organs containing tissue factor and phospholipids.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

How is thromboplastin obtained nowadays?

A

Recombinant thromboplastin.

32
Q

If a patient has a prolonged/elevated INR, which coagulation pathway is affected?

A

Extrinsic pathway

33
Q

What does APTT measure?

A

The clotting time of plasma after the activation of contact factors without adding tissue thromboplastin and indicates the efficiency of the intrinsic pathway.

34
Q

What factors are involved in the intrinsic pathway?

A

12, 11, 9, 8, 10, 2

35
Q

How is the plasma sample prepared for APTT test?

A
  • sample collected in trisodium citrate (9:1)
  • centrifuged
  • pre-incubated with a contact activator such as kaolin, silica.
  • calcium chloride is added - Time is measured
36
Q

What factor deficiencies will APTT detect?

A

All except for factor 7.

37
Q

What factors does the contact activator activate?

A

12 to 12 a which in turn cleaves 11 to 11a but stops here without calcium

38
Q

What is the reference range for APTT ?

A

25-45 seconds

39
Q

What does a prolonged APTT indicate?

A 
Haemophilia A (def 8)
Haemophilia B (def 9)
40
Q

Which is faster warfarin or heparin?

A

Heparin is faster.

41
Q

What is APTT also referred to as?

A

PTTK or KCT

42
Q

What is the intrinsic pathway?

A

12, 11, 9, 8 ,10, 2, fibrinogen

43
Q

What are APTT and PT used for?

A
  • patient monitoring on warfarin and heparin
  • screening for theatre
  • liver function
44
Q

What is the thrombin time test composed of?

A
  • trisodium citrate, centrifuge.
  • addition of thrombin
    (fibrinogen - fibrin)
  • 37C
45
Q

What is the normal range of TT?

A

15 - 19 seconds, should be within 2 secs

46
Q

What are some of the causes of a prolonged TT?

A

Hypofibrinogenemia (normal fibrin, not functional)
Raised conc of fibrinogen degradation products
Heparin presence

47
Q

What does TT measure?

A

The common pathway : 10, 5 , 2 and fibrinogen.

48
Q

What is the common pathway?

A

10, 5, 2, fibrinogen

49
Q

How is fibrinogen measured?

A

Clauss method

50
Q

What is the principle of the Clauss method?

A
  • Diluted patients plasma is clotted with a strong thrombin solution.
  • Owren’s buffer
  • Thrombin
51
Q

Why must the patients plasma be diluted for the Clauss method (fibrinogen measurement)?

A

To lower the concentrations of any products, fibrinogen degradation products of heparin which would interfere with the test.

52
Q

What is the normal fibrinogen range?

A

1.8 - 4.5g/L

53
Q

What is dysfibringoenemia?

A

This is where you have an abnormal fibrinogen molecule which will delay the conversion of fibrinogen to fibrin when using the Clauss clotting assay and so another method should be employed to measure the amount of fibrinogen such as in a patient’s sample.
Immunological assay needed

54
Q

What is normal platelets?

A

150 - 400 x10^9/L

55
Q

What are the 2 functions of VWF?

A

Platelet binding to collagen.

Carries and protects factor 8

56
Q

What is the most common hereditary bleeding disorder?

A

VWF

57
Q

How is abnormal VWF detected?

A

abnormal APTT levels - intrinsic pathway

58
Q

What does low D dimer mean?

A

Tells of abnormal or increased any time in thromboembolic events.
Negative predictor for DVT

59
Q

What does bleeding time analyse?

What is the principle?

A

Vascular integrity, how blood vessels are performing.
Homeostasis tester - depending on normal vascular function, normal platelet adhesion function and normal platelet numbers.

60
Q

What are some of the conditions associated with a prolonged bleeding time?

A

Inherited platelet function defects: Glanzmann’s Thrombasthenia

  • Bernard Soulier
  • Ehlers Danlos
61
Q

How is the bleeding time test done?

A 
Template BT - forearm blade.
Sphygmomanometer cuff (inflated to 40mmHg)
62
Q

What is the normal BT range:

A

2-10 minutes.

63
Q

What does BT assess in terms of different homeostasis functions?

A

Platelet function
Von WF
- does not affect the intrinsic and extrinsic factor def

64
Q

Where does the majority of thrombocytopenias come from?

A

Acute leukaemia, aplastic anemia, patients with malignancies who are on chemotherapy.

65
Q

what types of patient antibodies affect the thrombocytopenias?

A

ITP - antibodies against platelet antigen idiopathic thrombotic purpura
NAIP - Neonatal alloimmune thrombocytopenia.

66
Q

How are platelets counted?

A

Impedance or optically by light scatter.

67
Q

What is the manual platelt counter called?

A

Haemocytometer

68
Q

What is the threshold for patients to be given platelet pool transfusions prior to surgery?

A

Anything less than 100 x10^9/L, anything below 20 will be given platelet transfusions.

69
Q

Why are platelet adhesion tests rarely used for testing platelet function?

A

Lack of platelet specificity, involved passing of blood through a Salzmann column (glass fibre beads)

70
Q

Which analyser is most commonly used to assess platelet function?

A

PFA-100, using citrated whole blood passing through a membrane coated with collagen and either ADP or adrenaline (platelet agonists)

71
Q

How does the PFA-100 analyser measure platelet function?

A

A drop in flow rate is monitored as platelets form a plug that seals the aperture. The time to form the closure of the aperture of the PFA analyser is referred to the closure time.

72
Q

What is the threshold for platelet dysfunction?

A

Prolonged closure time or even prevention of closure >300sec.
= Glanzmann Thrombasthenia, Bernard Soulier.

73
Q

What is the platelet aggregation test?

A

They measure the platelet aggregation function - involve preparing platelet rich plasma by centrifugation.
Red cells go to bottom, platelets stay in plasma ‘platelet rich plasma’, preparation of platelet poor plasma by spinning of sample.

74
Q

What are examples of platelet agonists which are used in platelet function tests?

A

ADP, collagen and Ristocetin.

75
Q

What is an example of a drug which inhibits aggregation in patients with cardiac thrombotic disorders ?

A

Aspirin and Clopidogrel

Haematology and Transfusion Science (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions