A routine coagulation test run by Awanui labs includes the following component tests:
- PT
- aPTT
- Fibrinogen
- +/- INR
Prothrombin time (9-13s)
The prothrombin time is a measure of extrinsic pathway activity.
Causes of prolonged PT
- Warfarin (and other vitamin K agonists)
- Vitamin K deficiency
- Hepatosis
- DIC
Activated partial thromboplastin time (20-31s)
The aPTT is a measure of intrinsic pathway activity.
Causes of prolonged aPTT
- Haemophilia A, B, or C
- von Willebrand disease
- Heparin
- Severe hepatosis (see FVIII)
- DIC
- Antiphospholipid syndrome (APS) causes a paradoxical increase in aPTT in vitro despite producing a hypercoagulable state*
Fibrinogen (1.7-4.3g/L)
Hypofibrinogenaemia is either consumptive or due to a production deficit:
- DIC
- Liver disease
- Transfusion
Hyperfibrinogenaemia may be an acute phase response:
- Inflammation
- Pregnancy
- Cancer
- Trauma
Fibrinogen concentration is typically tested for with immunoassays or the Clauss fibrinogen assay.
International normalised ratio
The INR is a standardised measure of PT. The normal INR is 0.8-1.2. The therapeutic range in 2.0-3.0.