The Coagulation Panel

Question 1

What is Haemostasis?

Answer 1

Process to fix a break in blood vessel wall

Question 2

How are coagulation factors involved in secondary haemostasis measured?

Answer 2

• Blood contained in citrate tube
• Spin blood, set off the coagulation cascade
• Visually look for a clot
• Automated system detects light penetration (as fibrinogen becomes fibrin and strands start to crosslink the mixture gets cloudy and machine detects this)

Question 3

What is PT?

Answer 3

Prothrombin time measured in seconds

Question 4

What is APTT?

Answer 4

activated partial thromboplastin time measured in seconds

Question 5

What is Fibrinogen?

Answer 5

beware derived versus measured, measured in g/L

Question 6

What is INR?

Answer 6

Internationally standardised ratio based on the PT, technically only valid for warfarin

Question 7

What are results affected by?

Answer 7

sampling issues and other interferences in the test tube

Question 8

What are DOACs?

Answer 8

Direct- acting oral anticoagulants
Rivaroxaban/ apixaban

Question 9

Where does DOAC act?

Answer 9

Factor X (prevents from activating)
IIa

Question 10

What DOACs affect factor X?

Answer 10

apixaban
rivaroxaban

Question 11

What DOACs act on IIa?

Answer 11

dabigatran

Question 12

What is the benefit of DOACs?

Answer 12

• Don’t need routine monitoring of levels
• Standard dose
• Act on factor X prevents it from becoming activated
• Means no prothrombin to thrombin which means no fibrinogen= prevents a clot
• Act on fac 2 directly

Question 13

How DOACs affect coag panel tests?

Answer 13

Variable non- linear impact of PT & APTT

Question 14

What clinical scenarios are DOACs used?

Answer 14

Blood clots

Question 15

What does Warfarin inhibit?

Answer 15

Inhibits activity of vitamin K
Vitamin K dependent clotting factors= inhibited

Question 16

What vitamin K dependent clotting factors are there?

Answer 16

IX, VII, X, II= inhibited

Question 17

How does Warfarin affect the coag panel?

Answer 17

• Warfarin affects both PT & APTT
• INR is standardised way of reporting PT
• Use INR to adjust warfarin dosing

Question 18

What is PT sensitive to?

Answer 18

• PT is particularly sensitive to the clotting factors affected by warfarin so can be used to accurately monitor the degree of warfarin- induced anticoagulation

Question 19

What clinical scenarios is warfarin used for?

Answer 19

Blood clots

Question 20

What are Heparins?

Answer 20

• Naturally occurring sulphated glycosaminoglycans isolated from animal tissue, most commonly porcine intestine

Question 21

What do heparins do?

Answer 21

• Indirectly inhibit blood coagulation, by potentiating the anticoagulant effect of antithrombin x2000
• Accelerates the inactivation of thrombin (IIa) & factor Xa

Question 22

What is the unfractionated heparin?

Answer 22

• Can bind to both antithrombin (AT) & thrombin (IIa)
• Given intravenously
• Requires a loading dose before continuous infusion
• Requires careful monitoring

Question 23

What is low molecular weight heparin?

Answer 23

• Smaller molecular size
• Binds antithrombin and potentiates its inhibitory effect on Xa
• Cannot bind thrombin (IIa)
• Subcut injection
• More predictable pharmacokinetics
• Weight dependent dosing

Question 24

How does Heparin affect coag panel tests?

Answer 24

• UFH affects APTT
• Adjust dosing using APTT ratio
• LMWH also affects APTT but less sensitively, depends on chain length of the LMWH, longer chain= more APTT prolongation

Question 25

What is an example of a Thrombolytic?

Answer 25

tPA

Question 26

What are the uses of thrombolytics?

Answer 26

Thrombolysis= "clot buster" medicine Systemic versus catheter- directed thrombolysis

Question 27

What clinical cases are Thrombolytics used for?

Answer 27

- Massive PE with haemodynamic instability - Acute ischaemic stroke - Blocked CVC line - Acute limb ischaemia

Question 28

Do antiplatelets affect coag panel tests?

Answer 28

NO

Question 29

What are the uses of antiplatelets?

Answer 29

- Primary prevention- high cardiovascular risk score - Secondary prevention- after MI, stroke, PCI/ stenting, PVD, arterial thrombosis - No effect on clotting cascade - Involved in primary haemostasis - stop platelets being so sticky

Question 30

What is Haemophilia A?

Answer 30

- X- linked - Recessive - Mainly affects males - Problem with factor 8 (severe end= no factor 8)

Question 31

What is Haemophilia B?

Answer 31

- Affects gene which makes factor 9 - Recessive - X linked - Rarer

Question 32

What are the symptoms of Haemophilia?

Answer 32

Both can cause huge pregnancy complications, huge risk of bleeding Haemorrhages, excessive brusing

Question 33

What is the treatment for Haemophilia?

Answer 33

Preventative drugs which stop bleeding

Question 34

What does Von willebrand's disease affect?

Answer 34

- Important in primary and secondary haemostasis

Question 35

How does vwb affect primary haemostasis?

Answer 35

Binds platelets Binds exposed endothelium Forms adhesive bridge between vascular endothelium & platelets Forms platelet plug

Question 36

How does VWD affect secondary haemostasis?

Answer 36

As it is a carrier for FVIII in the blood (otherwise FVIII would be rapidly degraded in the circulation)

Question 37

What different types of vWB disease are there?

Answer 37

Quantitive (low levels) Qualitative (abnormal function)

Question 38

What can happen to APTT in VWB?

Answer 38

APTT can be prolonged in some forms of more severe VWB due to the resulting low FVIII levels

Question 39

What are symptoms of VWD?

Answer 39

Spectrum of severity Often mucosal bleeding

Question 40

What is DIC?

Answer 40

Disseminated intravascular coagulopathy

Question 41

What happens in DIC?

Answer 41

-Dysregulation of normal process of haemostasis -Balance of clotting versus bleeding (fibrinolytic) tendency - Generation and deposition of fibrin

Question 42

What are the 2 stages of DIC?

Answer 42

Overactive clotting followed by bleeding - Initially prothrombotic, as things continue the clotting factors & platelets get used up leading to bleeding symptoms

Question 43

How do you treat DIC?

Answer 43

Identify underlying cause: - Severe sepsis - Malignancies - Obstetric complications - Trauma - Severe burns - Liver failure - Pancreatitis - CAPS - heat stroke/ hyperthermia Blood product support as required