what is the reference range for PT prothrombin time?
12-16 seconds
what are the 6 most likely causes of elevated PT (above 16 secs)?
- Vitamin K def.
- Drugs such as Warfarin (anticoagulants)
- Factor Xa inhibitors
- Factor IIa (thrombin) inhibitors
- liver disease
- malabsorption (leading to VK def)
reverence range for Activated Partial Thromboplastin Time (APTT)
27-35 seconds
what are the 6 most likely causes of elevated APTT (above 35 secs)?
- Deficiencies of Factors XII, XI, IX or VIII
- Lupus anticoagulant (LA) - targets phospholipids
- Acquired clotting factor inhibitors
what are the 2 likely issues of low APTT (below 27)?
- acute phase response = high FVIII
- sample collection issues
likely causes if BOTH PT and APTT are elevated
Vitamin K def.
Liver disease due to malabsorption or clotting factor inhibitors
thrombin inhibitors
DIC - consumption of clotting factors
which coagulation pathway does FIB fibrinogen measure?
common pathway (from Xa onwards)
Fibrinogen (Fib) Reference range
1.5 - 4.0 g/l
likely causes of Reduced FIB (<1.5 g/l)
Liver disease
DIC - consumption of clotting factors
Transfusion
inherited deficiencies
likely causes of Increased FIB (>4.0 g/l)
Age
Pregnancy
Birth control (oral)
Disseminated malignancy
Thrombin time (TT) Reference range
13-15 seconds
what does Thrombin Time (TT) measure?
common pathway
(TT is Indirectly proportional to Fib)
low fib = high tt and vice versa
Thrombin time TT ref range
13-15 sec
acquired causes of increased TT and decreased fib
inherited causes of increased TT and decreased fib
