Coagulation Studies

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Rationale

- Assessment of bleeding diathesis

- Assessment of efficacy of anti-coagulants

 

Procedure

- Venepuncture: blue tube

 

Tests

- PT

-  INR

- APTT

- Mixing Test

- Bleeding Time

- Coagulation Factors

- Ristocetin

 

 

 

Prothrombin Time (PT)

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Features

- Tests extrinsic & common pathways

- Factors II, V, VII, IX & fibrinogen

- Prolongation indicates:

-  Warfarin therapy

-  Liver damage

-  Vitamin K deficiency

-  Factor V Leiden

- International Normalised Ratio (INR)

-  Compares pts PT to normal pts PT as ratio

-  Normal 1 – 1.5

-  Used to monitor Warfarin therapy

-  Therapeutic range around 2.0 – 3.0

 

 

 

APTT (Activated Partial Thromboplastin Time)

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Features

- Tests intrinsic & common pathways

- Factors VIII, IX, XI

- Used to monitor Heparin therapy

-  Not Enoxaparin

- Prolongation indicates

-  Heparin therapy

-  Antiphospholipid Ab

-  Coagulation factor deficiency: VIII (Haemophillia A), IX, XI

-  Mixing test to DDx

 

 

 

Mixing Test

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Features

- Used to determine the cause of prolonged APTT if not on Heparin

- Pts serum mixed w normal plasma

- If APTT corrects once mixed indicates serum based problem ie: Antiphospholipid Ab

 

 

 

Bleeding Time

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Coagulation Factors

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