Coagulation Tests

Question 1

What are the 4 main coagulation tests?

Answer 1

• Activated Partial Thromboplastin Time (APTT)
• Prothrombin Time (PT)
• Bleeding Time
• Reptilase Time

Question 2

What is the APTT test?

Answer 2

• Tests clotting factors involved in the intrinsic pathway of the coagulation cascade

=> These clotting factors include:

• Factor I
• Factor II
• Factor V
• Factor VIII
• Factor X
• Factor XI
• Factor XII

=> If all clotting factor levels are normal, clots take 30-40 seconds to form

Question 3

What are the causes of a prolonged APTT?

Answer 3

• Haemophillia A (Factor VIII deficiency)
• Haemophillia B (Factor IX deficiency)
• Disseminated Intravascular Coagulation
• Use of heparin

Question 4

What is the PT test?

Answer 4

• Tests clotting factors involved in the extrinsic and common pathways of the coagulation cascade

=> These clotting factors include:

• Factor I
• Factor II
• Factor VII
• Factor IX
• Factor X

=> A normal PT is 11-13 seconds

Question 5

What are the causes of a prolonged PT?

Answer 5

• Warfarin
• Vitamin K Deficiency
• Disseminated Intravascular Coagulation
• Sepsis
• Severe liver disease

=> Clotting factors II, VII, IX, and X are all vitamin K dependant

Question 6

What is Bleeding time?

Answer 6

• Used to assess the overall ability of a clot to form
• Small incision made in the patients skin and the time taken for a clot to form and bleeding to stop is measured

=> Normal time is 3-10 minutes

Question 7

What are the causes of a prolonged Bleeding Time?

Answer 7

• Thrombocytopenia
• Uraemia
• Disseminated Intravascular Coagulation
• Von Williebrand Disease
• Aspirin use

Question 8

What is the Relaptilase Time?

Answer 8

• Relaptilase is an enzyme that has a similar action to thrombin but is not affected by antithrombin III
• Test requires no additional constituents and is used to identify any deficiencies in fibrinogen

Question 9

What are the causes of a prolonged Relaptilase Time?

Answer 9

• Inherited
• Hypofibrinogenaemia/dysfibrinogenaemia
• Liver disease
• Disseminated Intravascular Coagulation
• Hypoalbuminaemia

Question 10

What factors are affected by Heparin use?

Answer 10

• Factor II
• Factor IX
• Factor X
• Factor XI

Question 11

What factors are affected by Warfarin?

Answer 11

• Factor II
• Factor VII
• Factor IX
• Factor X

Question 12

What factors are affected in DIC?

Answer 12

• Factor I
• Factor II
• Factor V
• Factor VIII
• Factor XI

Question 13

What factors are affected in Liver Disease?

Answer 13

• Factor I
• Factor II
• Factor V
• Factor VII
• Factor IX
• Factor X
• Factor XI

Question 14

What are the blood clotting results in vitamin K deficiency?

Answer 14

APTT increase
PT increase
Bleeding time normal

Question 15

What are the clinical features of platelet disorders (VWD) in terms of:

• Site of bleeding
• Petechiae
• Bruises
• Muscle bleeding
• Bleeding after cuts and scatches
• Bleeding after surgery or trauma

Answer 15

=> Site of bleeding

• Skin
• Mucous membranes

=> Petechiae - Present

=> Bruises - Small and superficial

=> Muscle bleeding - Rare

=> Bleeding after cuts and scratches - Yes

=> Bleeding after surgery or trauma - Mild and immediate

Question 16

What are the clinical features of coagulation factor deficiency in terms of:

• Site of bleeding
• Petechiae
• Bruises
• Muscle bleeding
• Bleeding after cuts and scatches
• Bleeding after surgery or trauma

Answer 16

=> Site of bleeding
- Deep in soft tissues

=> Petechiae - No

=> Bruises - Large and deep

=> Muscle bleeding - Common

=> Bleeding after cuts and scratches - No

=> Bleeding after surgery or trauma - Often severe but delayed