Approach To Haemostasis

Question 1

What is haemostasis?

Answer 1

The physiological process that stops bleeding through blood vessel constriction, platelet plug formation, and fibrin clot stabilization.

Question 2

What occurs during primary haemostasis?

Answer 2

Platelet adhesion, activation, and aggregation to form a temporary plug at the site of injury.

Question 3

What is the role of secondary haemostasis?

Answer 3

Activates the coagulation cascade to generate fibrin, stabilizing the platelet plug into a firm clot.

Question 4

What are platelets and what is their function?

Answer 4

Cell fragments that initiate clotting by forming the primary plug at injury sites.

Question 5

What is von Willebrand Factor (vWF)?

Answer 5

A glycoprotein that helps platelets adhere to damaged endothelium and stabilizes factor VIII in circulation.

Question 6

What are coagulation factors?

Answer 6

Plasma proteins that activate sequentially to form fibrin in the coagulation cascade.

Question 7

What does thrombin do in haemostasis?

Answer 7

Converts fibrinogen into fibrin to form a stable clot.

Question 8

What is fibrinolysis?

Answer 8

The breakdown of fibrin clots by plasmin to regulate clot size.

Question 9

What does Antithrombin III do?

Answer 9

Inhibits thrombin and factor Xa to prevent excessive clotting.

Question 10

What triggers the extrinsic pathway?

Answer 10

Tissue Factor (TF) released upon vascular injury.

Question 11

What initiates the intrinsic pathway?

Answer 11

Contact with exposed collagen and negatively charged surfaces.

Question 12

What is the common pathway?

Answer 12

The convergence of intrinsic and extrinsic pathways, leading to fibrin formation.

Question 13

What is DIC (Disseminated Intravascular Coagulation)?

Answer 13

A condition of systemic clotting that depletes platelets and factors, leading to bleeding.

Question 14

What is ITP (Immune Thrombocytopenic Purpura)?

Answer 14

An autoimmune disorder where antibodies destroy platelets.

Question 15

What is TTP (Thrombotic Thrombocytopenic Purpura)?

Answer 15

A condition due to ADAMTS13 deficiency, causing widespread platelet-rich thrombi.

Question 16

What is aplastic anaemia?

Answer 16

Bone marrow failure leading to pancytopenia, including low platelet production.

Question 17

What is hypersplenism?

Answer 17

Overactive spleen that sequesters and destroys platelets.

Question 18

What does Prothrombin Time (PT) measure?

Answer 18

The extrinsic and common pathways of coagulation.

Question 19

What does Activated Partial Thromboplastin Time (aPTT) measure?

Answer 19

The intrinsic and common coagulation pathways.

Question 20

What is the role of fibrin?

Answer 20

Forms an insoluble mesh that stabilizes the platelet plug into a solid clot.

Question 21

A 25-year-old man presents with excessive bleeding after a tooth extraction.
1. What are two broad components of haemostasis that could be defective in this case?

2. Platelet count is normal; PT is normal; aPTT is prolonged. Which haemostatic pathway is likely affected?

3.Further tests reveal low Factor VIII levels. What is the most likely diagnosis?

Answer 21

1. Platelet function (primary haemostasis) and coagulation cascade (secondary haemostasis).
2. Intrinsic pathway
3. Haemophilia A

Question 22

1. A 16-year-old girl reports easy bruising and frequent nosebleeds. What is the first investigation you’d order?
2. Platelet count is low; PT and aPTT are normal. What category of haemostatic defect does this suggest: primary or secondary?

3.Bone marrow biopsy shows normal megakaryocytes. What is the most likely diagnosis?

Answer 22

1. Full blood count including platelet count and coagulation screen (PT, aPTT).
2. Primary haemostatic defect.
3. Immune Thrombocytopenic Purpura (ITP).

Question 23

1. A woman develops severe bleeding 6 hours after delivery. She has petechiae and oozing from IV sites. What condition should be high on your differential?
2. Labs show prolonged PT and aPTT, low fibrinogen, high D-dimer, and thrombocytopenia. What is the pathophysiological mechanism behind this condition?
3. What is the cornerstone of treatment?

Answer 23

1. Disseminated Intravascular Coagulation (DIC).
2. Widespread activation of clotting → consumption of platelets and coagulation factors → secondary bleeding.
3. Treat the underlying cause (e.g., sepsis, placental abruption) and provide supportive care (e.g., FFP, platelets, cryoprecipitate).

Question 24

1. A 34-year-old woman develops fever, confusion, renal failure, and widespread purpura. What are two possible haematological emergencies you would consider?
2. Labs show thrombocytopenia and schistocytes on blood smear. What specific test would help confirm TTP?
3. What is the mainstay of treatment for TTP?

Answer 24

1. Thrombotic Thrombocytopenic Purpura (TTP), Disseminated Intravascular Coagulation (DIC).
2. ADAMTS13 activity test.
3. Plasma exchange (plasmapheresis).

Question 25

1. A 29-year-old woman has had two miscarriages and presents now with DVT. What inherited or acquired clotting disorder should you suspect? 2. Lupus anticoagulant and anticardiolipin antibodies are positive. What is the name of this condition? 3. How does this condition paradoxically lead to both clotting and prolonged aPTT?

Answer 25

1. Antiphospholipid Syndrome (APS). 2. Antiphospholipid Syndrome. 3. Autoantibodies interfere with phospholipid-dependent coagulation tests (like aPTT), falsely prolonging them despite a pro-thrombotic state.