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MICN201 2025 Blood > Haemostasis 3 Laboratory Tests of Haemostasis & Introduction to Bleeding Disorders > Flashcards

Haemostasis 3 Laboratory Tests of Haemostasis & Introduction to Bleeding Disorders Flashcards

1
Q

What is plasma?

A

A liquid component of blood that contains fibrinogen when anticoagulants are used

In contrast, serum is clotted blood without fibrinogen.

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2
Q

What anticoagulant is typically used for clotting assays?

A

Sodium citrate (blue top) tubes with a ratio of 1:9 of citrate to blood.

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3
Q

What is the reference interval for Prothrombin Time (PT)?

A

9 - 13 seconds.

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4
Q

What does the International Normalised Ratio (INR) correct for?

A

Differences between PT kits, especially differences in Tissue Factor.

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5
Q

What factors are detected by a prolonged Prothrombin Time (PT)?

A

Deficiency of FVII, FX, FV.

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6
Q

What is the normal range for Activated Partial Thromboplastin Time (APTT)?

A

22 - 34 seconds.

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7
Q

What factors are detected by a prolonged APTT?

A

Deficiency of VIII, IX, XI, X, V.

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8
Q

What is the reference interval for fibrinogen concentration?

A

1.8 - 4.0 g/L.

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9
Q

What are the clinically important factor deficiencies detected by APTT and PT?

A
  • APTT: VIII, IX, XI
  • PT: VII
  • Fibrinogen: fibrinogen levels.
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10
Q

What are common causes of prolonged bleeding?

A
  • Defective vessel wall disorders
  • Platelet disorders
  • Coagulation disorders.
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11
Q

What is the reference interval for platelet count?

A

150 - 400 x 10^9/L.

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12
Q

What is von Willebrand disease characterized by?

A

Low levels or abnormal vWF molecule leading to reduced platelet adhesion and prolonged bleeding.

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13
Q

What are the key components in assessing bleeding disorders?

A
  • History of bleeding location
  • Pattern of bleeding
  • Drug history and diet
  • Family history.
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14
Q

What tests are included in a coagulation screen?

A
  • APTT
  • PT
  • Fibrinogen.
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15
Q

What is the inheritance pattern of haemophilias?

A

X-linked disorders.

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16
Q

What are the factor levels associated with bleeding severity in haemophilia?

A
  • Severe: ≤1%
  • Moderate: 2-5%
  • Mild: 5-50%.
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17
Q

What is the treatment for haemophilia A?

A

Intravenous infusion of recombinant FVIII.

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18
Q

What is the role of Vitamin K in coagulation?

A

Needed for the final stage of producing functional Factors II, VII, IX, X, and Proteins C & S.

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19
Q

What can cause Vitamin K deficiency?

A
  • Low intake
  • Antibiotics
  • Malabsorption disorders.
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20
Q

What is the risk associated with Vitamin K deficiency in neonates?

A

Increased risk of Vitamin K Deficiency Bleeding, especially gastrointestinal and brain.

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21
Q

What are common clinical causes for warfarin treatment to go out of control?

A
  • Changed intake of vitamin K
  • Decreased absorption of vitamin K
  • Change in warfarin clearance by the liver.
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22
Q

What is Disseminated Intravascular Coagulation (DIC)?

A

Widespread activation of platelets and coagulation in blood leading to coagulopathy.

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23
Q

What are the clinical signs of DIC?

A
  • Bleeding
  • Thromboses and ischaemia.
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24
Q

What causes prolonged PT and APTT in adults?

A

Vitamin K deficiency.

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25
What is the treatment for severe haemophilia A?
Emicizumab monoclonal antibody, administered subcutaneously.
26
What is the significance of the INR for patients on warfarin?
Target range is 2.0 - 3.0.
27
What is the normal reference range for D-dimers?
<500 ug/L
28
What is the current platelet count mentioned?
80 x10^9/L
29
What was the platelet count 24 hours ago?
225 x10^9/L
30
What is the primary cause of Disseminated Intravascular Coagulation (DIC)?
Tissue factor and other cell products released into blood vessels
31
What are the clinical features of DIC?
Bleeding and/or microvascular thromboses
32
What laboratory findings indicate consumptive coagulopathy in DIC?
* Falling fibrinogen level * Falling platelet count * Increasing PT and APTT * High/rising level of fibrin degradation products (D-dimers)
33
Which infections are known to cause DIC?
Gram negative septicaemia
34
What activates monocytes in gram negative septicaemia?
Endotoxin
35
What severe conditions can cause DIC?
* Any severe or widespread tissue injury * Prolonged shock with secondary hypoxic tissue injury * Extensive tissue trauma * Severe burns * Severe viral infections * Traumatic brain injury
36
What are less common causes of DIC?
* Obstetric complications (amniotic fluid embolism, placental abruption, intrauterine fetal death) * Severe allergic hypersensitivity reactions * Malignancy (some acute leukaemias, mucin-secreting adenocarcinomas)
37
What is the primary treatment for acute DIC?
Treat the underlying cause
38
What is the reference interval for fibrinogen levels?
1.8-4.0 g/L
39
What anticoagulant is used to obtain plasma for clotting assays?
Sodium citrate
40
What does the Prothrombin Time (PT) test measure?
The extrinsic pathway of coagulation
41
What is the target INR range for patients on warfarin?
2.0 – 3.0
42
What does a prolonged APTT indicate?
Deficiency of coagulation factors VIII, IX, XI, X, V
43
What is the reference interval for APTT?
22-34 sec
44
What does a fibrinogen assay measure?
The concentration of fibrinogen in plasma
45
What are common causes of prolonged bleeding?
* Defective vessel wall disorders * Platelet disorders (thrombocytopenia) * Coagulation disorders
46
What tests are included in the coagulation screen?
* APTT * PT * Fibrinogen
47
What are the inherited disorders of haemophilia characterized by?
X-linked disorders affecting males
48
What is the clinical problem associated with haemophilia?
Increased bleeding due to reduced clot formation
49
What is the treatment for severe haemophilia A?
Intravenous infusion of recombinant FVIII
50
What is the main risk factor for Vitamin K deficiency?
Low intake, antibiotics, or malabsorption disorders
51
What vitamin is essential for the production of functional Factors II, VII, IX, and X?
Vitamin K
52
What is the risk of Vitamin K deficiency in neonates?
Vitamin K Deficiency Bleeding, especially gastrointestinal and brain
53
What is the common treatment for Vitamin K deficiency in neonates?
0.5 mg IM at birth or 3 oral doses
54
What are the low levels of Vitamin K-dependent factors present at birth associated with?
Risk of bleeding (Vitamin K Deficiency Bleeding) especially gastrointestinal and brain ## Footnote ~1:10 000 (in high-income countries)
55
What is the recommended dose of Vitamin K given after birth?
0.5 mg IM at birth or 3 oral doses, poorly absorbed even by full-term normal infant
56
Why do premature infants require an intramuscular dose of Vitamin K?
They are not able to absorb sufficient Vitamin K
57
What is the effect of Warfarin on Vitamin K?
Warfarin inhibits Vitamin K
58
List the benefits of Warfarin anticoagulation
* Useful for treating venous clots * Prevents clots on heart valves * Used in atrial fibrillation * Oral medicine * Widely used for many decades
59
What are the potential problems associated with Warfarin anticoagulation?
* Risk of bleeding if excessive anticoagulation * Risk of clotting if insufficient anticoagulation * A narrow therapeutic window exists
60
What does INR stand for in the context of Warfarin treatment?
International Normalised Ratio
61
What are typical laboratory results for someone taking Warfarin?
* PT: 26 (9 - 13 s) * INR: 2.5 (2.0-3.0 therapeutic range) * APTT: 42 (22 - 34 s)
62
What can cause warfarin treatment to go out of control?
* Changed intake of vitamin K in food * Decreased absorption of vitamin K * Change in warfarin clearance by the liver
63
What is Disseminated Intravascular Coagulation (DIC)?
Widespread activation of platelets and coagulation in blood
64
What are the clinical features of DIC?
* Variable, determined by the underlying condition * Bleeding and/or microvascular thromboses
65
What laboratory findings are associated with consumptive coagulopathy in DIC?
* Falling fibrinogen level * Falling platelet count * Increasing PT and APTT * High/rising level of D-dimers
66
What are common causes of DIC?
* Infections (e.g., gram negative septicaemia) * Severe tissue injury * Prolonged shock with secondary hypoxic tissue injury * Severe burns * Severe viral infections
67
What is a less common cause of DIC?
* Obstetric complications * Severe allergic hypersensitivity reactions * Malignancy
68
What is the primary treatment for acute DIC?
Treat the cause (if possible) and the DIC will stop
69
What should be done if secondary bleeding is caused by DIC?
* Replacement with appropriate blood component * Platelet transfusion for thrombocytopenia * Cryoprecipitate for low fibrinogen * Plasma infusion for severe bleeding with prolonged APTT

MICN201 2025 Blood (9 decks)

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