Normal Coagulation Pathway and Lab Tests

•    PT: extrinsic pathway (VII)

•    aPTT: intrinsic pathway (VIII, IX, XI, XII)

•    TT: fibrinogen to fibrin

•    Mixing study: differentiates factor deficiency from inhibitor

Haemophilia A and B

•    X-linked recessive

•    A: Factor VIII deficiency; B: Factor IX deficiency

•    Haemarthroses, deep bleeding

•    Prolonged aPTT, normal PT

•    Rx: factor replacement

von Willebrand Disease (vWD)

•    Most common inherited bleeding disorder

•    ↓ vWF → ↓ platelet adhesion & ↓ factor VIII

•    Mucocutaneous bleeding, menorrhagia

•    Rx: desmopressin (mild), vWF concentrate (severe)

Disseminated Intravascular Coagulation (DIC)

•    Trigger: sepsis, trauma, malignancy, obstetric catastrophe

•    Labs: ↓ fibrinogen, ↑ D-dimer, ↓ platelets, prolonged PT/aPTT

•    Rx: treat cause, FFP/cryoprecipitate, platelets if bleeding

Vitamin K and Clotting Factor Deficiencies

•    Affects II, VII, IX, X (extrinsic/intrinsic)

•    Causes: warfarin, liver disease, malabsorption

•    Prolonged PT > aPTT

•    Rx: vitamin K, FFP if active bleeding

Acquired Bleeding Disorders

•    Causes: liver disease, uraemia, anticoagulants, DIC

•    Always review medications (especially anticoagulants and antiplatelets)

Mixing Studies and Inhibitor Screening

•    Correction = factor deficiency

•    No correction = inhibitor (e.g. lupus anticoagulant, acquired haemophilia)