Coagulation testing

Question 1

what is the reference range for PT prothrombin time?

Answer 1

12-16 seconds

Question 2

what are the 6 most likely causes of elevated PT (above 16 secs)?

Answer 2

• Vitamin K def.
• Drugs such as Warfarin (anticoagulants)
• Factor Xa inhibitors
• Factor IIa (thrombin) inhibitors
• liver disease
• malabsorption (leading to VK def)

Question 3

reverence range for Activated Partial Thromboplastin Time (APTT)​

Answer 3

27-35 seconds​

Question 4

what are the 6 most likely causes of elevated APTT (above 35 secs)?

Answer 4

• Deficiencies of Factors XII, XI, IX or VIII​
• Lupus anticoagulant (LA) - targets phospholipids
• Acquired clotting factor inhibitors

Question 5

what are the 2 likely issues of low APTT (below 27)?

Answer 5

• acute phase response = high FVIII
• sample collection issues

Question 6

likely causes if BOTH PT and APTT are elevated

Answer 6

Vitamin K def.
Liver disease due to malabsorption or clotting factor inhibitors
thrombin inhibitors
DIC - consumption of clotting factors

Question 7

which coagulation pathway does FIB fibrinogen measure?

Answer 7

common pathway (from Xa onwards)

Question 8

Fibrinogen (Fib)​ Reference range

Answer 8

1.5 - 4.0 g/l​

Question 9

likely causes of Reduced FIB (<1.5 g/l)

Answer 9

Liver disease
DIC - consumption of clotting factors
Transfusion
inherited deficiencies

Question 10

likely causes of Increased FIB (>4.0 g/l)

Answer 10

Age
Pregnancy
Birth control (oral)
Disseminated malignancy

Question 11

Thrombin time (TT) Reference range

Answer 11

13-15 seconds​

Question 12

what does Thrombin Time (TT) measure?

Answer 12

common pathway
(TT is Indirectly proportional to Fib)
low fib = high tt and vice versa

Question 13

Thrombin time TT ref range

Answer 13

13-15 sec

Question 14

acquired causes of increased TT and decreased fib

Question 15

inherited causes of increased TT and decreased fib