Brainscape's Knowledge GenomeTM

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


See full index

_MS2 HemeOnc > 8/19- Bleeding Pt and Tests of Hemostasis > Flashcards

8/19- Bleeding Pt and Tests of Hemostasis Flashcards

1
Q

OVERVIEW:

Hemostasis Testing Involves:

Coagulation factors

  • PT (prothrombin time), PT INR
  • PTT (activated partial thromboplastin time)
  • PT/PTT mixing study
  • Fibrinogen
  • Thrombin time
  • Coagulation factor assay

Lupus anticoagulant assay

Fibrinolysis

  • D-dimer

Platelet function test

  • Platelet aggregation study
A

(:

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

A functional assay is performed using what part of the blood?

A

Plasma

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

What is citrate? How does it work?

A

Citrate is an anticoagulant that works by chelating calcium

  • It is used in the performance of a functional assay to separate out the plasma
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Process of performing a functional assay on plasma?

A
  • Use citrate as anticoagulate (chelates Ca)
  • Centrifuge -> supernatant = platelet poor plasma (PPP)
  • PPP contains very small amt of platelets
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Antigenic assay is usually performed using what part of the blood?

A

Serum

  • Serum contains very small amt of coagulation factors and platelets
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the difference between plasma and serum?

A
  • Plasma contains coagulation factors and complements
  • Serum contains very few coagulation factors and complements since they go to a clot
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe the coagulation cascade

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

PT measures what coagulation factors? PTT?

A

PT: (7)

  • FVII

PTT: (8, 9, 11, 12)

  • FVIII
  • FVIX
  • FVXI
  • FVXII
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Which pathway is more sensitive to common pathway factors?

A

PT

  • When fibrinogen is 80 mg/dL, PT is prolonged but PTT is not
  • When fibrinogen is 25 mg/dL, PTT is also prolonged
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is INR? Why is it needed?

A

International Normalized Ratio

  • Designed to monitor pts who take warfarin as an anticoagulate
  • PT reagents differ in their sensitivity towards FII, FVII, and FX (2, 7, 10); PT from one lab may not be comparable to PT from another lab
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is thrombin time? When would it be prolonged?

A

Measures the conversion of fibrinogen to fibrin after addition of excess thrombin to undiluted plasma

Reasons for prolongation:

  • Heparin
  • Hypofibrinogenemia
  • Dysfibrinogenemia
  • Positive FSP (or D-dimer)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Process of fibrinogen assay?

A
  • Clauss assay (thrombin time based assay) is widely used = function fibrinogen
  • Thrombin and phospholipid is added to 1:10 diluted pt plasma
  • Initiate clotting by addition of Ca
  • Functional fibrinogen is inversely proportional to thrombin time
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How does functional fibrinogen correspond to thrombin time?

A

Functional fibrinogen is inversely proportional to thrombin time

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

What is the normal range of functional fibrinogen?

A

220-440 mg/dL

  • For surgery or delivery, minimum fibrinogen required is 200 mg/dL
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is FDP? FSP?

A
  • FDP- fibrin degradation prodcuts
  • FSP- fibrin split products
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Causes of Prolonged PT/PTT (broad list)?

A

1. Factor deficiency

  • Decreased synthesis
  • Increased consumption
  • Dilutional coagulopathy (massive transfusion)

2. Circulating inhibitor

3. Adsorption of FX by amyloid

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

What are factor deficiencies that involve decreased synthesis?

A
  • Congenital factor deficiency (usually 1 factor)
  • Liver failure (all factors except FVIII and FXIII (8 and 13))
  • Vitamin K deficiency (FII, FVII, FIX, FX) (2, 7, 9, 10)
  • Warfarin (FII, FVII, FIX, FX) (2, 7, 9, 10)
  • Transient deficiency
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are factor deficiencies that involved increased consumption?

A
  • DIC (all factors)
  • Massive thrombosis (all factors)
19
Q

What are some examples of circulating inhibitor contributing to prolonged PT/PTT?

A
  • Factor specific inhibitor
  • Lupus anticoagulant
  • Anticoagulant such as heaprin, LMW heparin, and thrombin inhibitor
20
Q

What are the steps you should take in a prolonged PT/PTT work up?

A

1st

  • Repeat in an optimal condition
  • Rule out possible anticoagulant use (heparin removal)

2nd

  • PT/PTT mixing study
  • Individual factor assay
  • Assay for lupus anticoagulant
21
Q

Principles of a mixing study?

A
  1. If an inhibitor is present, it will inhibit normal and pt plasma, AND
  2. That 50% of any factor is enough to yield a normal test result. In fact, 20-40% of the normal level of coagulation factor is generally sufficient to give a normal PT and PTT

Since they are screening tests, the result should be confirmed by factor assay and/or lupus anticoagulant assay

22
Q

What is Lupus Anticoagulant (LAC)?

A

Misnomer; not an anticoagulant and not always associated with SLE

  • Interferes with phospholipid-dependent coagulation tests such as PT and PTT
  • Does not specifically neutralize any coagulation factors -> LAC does NOT cause any bleeding in spite of prolonged PTT
23
Q

Presence of LAC is a risk factor for what?

A

Thrombosis

24
Q

LAC combined with what may cause bleeding?

A

LAC with concurrent factor II deficiency or immune thrombocytopenia

25
Q

Describe the assay for Lupus Anticoagulant

A

There is no “lupus anticoagulation test”

It is recommended to perform 2 tests for LAC:

1. DRVVT- dilute Russell’s viper venom test

2. Hexagonal phase phospholipid neutralization test

No gold standard for LAC

26
Q

Describe the Dilute Russell’s Viper Venom Test (DRVVT).

What are you looking for?

A

Looking for LAC

DRVVT Screen:

  • RVV activates F. X directly
  • The test is made more sensitive to LAC by dilute RVV and dilute phospholipids.

DRVVT Confirmatory

  • Contains more phospholipids which may neutralize LAC.
  • Take ratio of screen and confirmatory.
27
Q

Describe the Hexagonal Phase Phospholipid Neutralization Test. What are we looking for?

A

Looking for LAC

  • Tube 1 is a PTT
  • Tube 2 contains hexagonal phase phosphatidyl ethanolamine (PE) which may neutralize LAC
  • Equal volume of patient’s plasma, normal plasma, and PE are incubated for 5 min and then measure PTT.
  • Addition of normal plasma can correct factor deficiency
28
Q

Case)

  • 37 yo male with pre-op screening
  • PT: 13.2 s (normal 11.4-11.9)
  • PTT: 66.0 s (normal 23-37)

In the PTT mixing study:

  • 0 min 47.3 s - 90 min 51.3 s

Interpretation?

A
  • No correction at 0 min and after 90-min incubation.
  • The results are suggestive of the presence of a circulating inhibitor, most likely lupus anticoagulant
29
Q

Case cont’d)

Lupus Anticoagulant Assay performed

DRVVT:

  • Screen: 76.7 s
  • Confirm: 37.6 s

- What is S/C?

Positive or negative test result?

Hexagonal phase phospholipid neutralization test?

  • Tube 1: 96.5 s
  • Tube 2: 68.7 s

- Tube 1- Tube 2?

Positive or negative?

A

DRVVT

  • S/C: 2.04 s
  • Positive result (normal under 1.35)

Hexagonal phase phospholipid neutralization test

  • Tube 1 - Tube 2: 227.8 s
  • Positive result (normal under 8s)
30
Q

What is the use of specific coagulation factor assays be done?

A

Determine the extent to which the patient’s plasma corrects the clotting time of plasma deficient only in a particular clotting factor

  • Example: add patient plasma to factor VIII-deficient plasma and perform an PTT on the mix; compare result to standard
31
Q

Factor VIII assay example:

  • Calibration curve
  • Pt plasma
A
32
Q

Overview of platelet function

A
33
Q

Steps in platelet activation?

A
  • Activation
  • Shape change
  • Secretion (fibrinogen, vWF, ADP, Ca)
  • Aggregation
34
Q

What factors may activate platelets?

A

Agonists:

  • Thrombin
  • Collagen
  • ADP
  • Epinephrine
35
Q

What substances are secreted by activated platelets?

A
  • Fibrinogen
  • vWF
  • ADP
  • Calcium
36
Q

What is platelet Lumi-aggregometry?

A
37
Q

Platelet Aggregation Tracing?

A
38
Q

What does a typical platelet aggregation study look like?

A
39
Q

What may result in abnormal results of a platelet aggregation study?

A

Thrombocytopenia Platelet function tests:

  • Drugs, uremia, myeloproliferative disorders
  • Bernard-Soulier syndrome (ristocetin)
  • Glanzmann thrombasthenia (all agonists except ristocetin)
  • Storage pool disease (epinephrine and ADP)
  • von Willebrand disease (ristocetin)
40
Q

Summary:

  • Basic coagulation tests are PT, PTT, and fibrinogen.
  • PT is more sensitive to fibrinogen level and other common pathway factor levels.
  • Lupus anticoagulant is a risk factor for thrombosis.
  • Platelet aggregation study is one of the tests for platelet function.
A

(:

41
Q

T/F: When PT is prolonged, but PTT is normal, only possibility is low factor VII

A

False

  • Even if FX is low, PT may be low but PTT may be normal (due to sensitivity differences)
42
Q

T/F: Presence of lupus anticoagulant is a risk for bleeding

A

False

43
Q

T/F: When platelet aggregometry shows decreased maximal aggregation, you can conclude that the patient has platelet function defects

A

False

  • Need to rule out thrombocytopenia

_MS2 HemeOnc (33 decks)

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