Coagulation Screen Flashcards
Indications for performing a coagulation screen?
- confirm suspected coagulopathy
- monitor coagulation status of patient on anti-coagulants
- assess coagulation pre-surgery
- assess synthetic liver function
What activates the intrinsic clotting pathway?
Contact with a damaged surface
What activates the extrinsic clotting pathway?
The release of tissue factors
What is prothrombin time (PT)?
- Measure of time taken for blood to clot via EXTRINSIC pathway
- INR is standardised version of this
- Measure of overall clotting factor synthesis or consumption
What conditions can affect prothrombin time (PT)?
- liver disease
- disseminated intravascular coogulation
- vitamin K deficiency
- warfarin levels
What is activated partial thrombopalstin time (APTT)?
- measure of time taken for blood to clot via INTRINSIC pathway
- measure of overall clotting factor synthesis or consumption
- also indicates issues with factors VIII, vWF, IX, XI
Which conditions can increase bleeding time (finger prick)?
- von Willebrans disease (autosomal dominant)
- Benrard-Soulier syndrome
- TTP/ITP/HUS/DIC
- thrombocytopenia
Bleeding time measures formation of platelet plug.
What conditions can affect APTT?
- haemophilia A (VIII, x-linked recessive)
- haemophilia B (IX, x-linked recessive)
- haemophilia C (XI - autosomal recessive)
- von Willebrands disease
What type of disorder causes increased bleeding time (from finger prick test)?
Platelet specific disorders
What is thrombin time?
- Test of how fast fibrinogen is converted to fibrin by thombin.
- if prolonged, indicates sythetic issue or consumption issue
Vitamin K deficiency/Warfarin use:
- PT/INR
- APTT
- Bleeding time
- Platelet count
- PT/INR - raised
- APTT - raised
- BT - normal
- platelets - normal
BT: bleeding time (finger prick)
Haemophilia A/B/C:
- PT/INR
- APTT
- Bleeding time
- platelet count
- PT/INR - normal
- APTT - raised
- BT - normal
- platelets - normal
von Willebrand’s disease:
- PT/INR
- APTT
- Bleeding time
- Platelet count
- PT/INR - normal
- APTT - normal/raised
- BT - raised
- platelets - normal
Disseminated intravascular coagulation (DIC):
- PT/INR
- APTT
- Bleeding time
- Platelet count
- PT/INR - raised
- APTT - raised
- BT - raised
- Platelets - low
ITP/TTP/HUS
- PT/INR
- APTT
- Bleeding time
- Platelet count
Immune thrombocytopenic purpura (ITP)
Thrombotic thrombocytopenic purpura (TTP)
Haemolytic uraemic syndrome (HUS)
- PT/INR - normal
- APTT - normal
- BT - raised
- platelets - low
Symptoms of clotting disorders
- haemorthrosis
- muscle haematomas
- prolonged bleeding after dental surgery
Symptoms of platelet disorders
- petechiae
- bruising
- contact bleeding (e.g. gums)
- menorrhagia
