Exam Practical Blood

Question 1

Prothrombin Time

Answer 1

(Normal = 10-14 seconds)
This simple test measures the extrinsic pathway in addition to the common terminal sequence. Tissue thromboplastin and calcium are added to citrated plasma. The prothrombin time may also be expressed as the International Normalized Ratio (INR).

Question 2

Activated Partial Thromboplastin Time (APTT)

Answer 2

(Normal = 30-40 seconds)
his screening test assesses the intrinsic pathway of coagulation in addition to the common terminal sequence. In this test three substances are added to citrated plasma, to initiate coagulation: phospholipid, a surface activator such as kaolin, and calcium.

Question 3

Thrombin time (TT)

Answer 3

(Normal = 14-16 seconds)
Assesses the common terminal sequence. It is sensitive to a deficiency of fibrinogen (I) or to an inhibition of thrombin (IIa).

Question 4

Intrinsic Factors

Answer 4

XII 
XI 
IX
XIIa
Xia
 (Calcium ions VIII + PF3)
IXa

Question 5

Extrinsic Factors

Answer 5

Factor VII
(Calcium ions Tissue Factor)
Factor VIIa

Question 6

Common Pathway

Answer 6

X Calcium ions V + PF3
Prothrombin (II)
Fibrinogen Fibrinogen XIII
Xa
Thrombin (IIa) Fibrin
Crosslinked Fibrin

Question 7

Why is it rare for a Factor 13 deficiency?

Answer 7

F13 is a stabilising factor, so when we have APPT and PT we still have a clot, but if that clot were to breakdown in a little while, it may be 13.

Question 8

Deficiency of Vitamin K- dependent factors:

Answer 8

Haemorrhagic disease of the newborn;
Biliary obstruction
Malabsorption of vitamin K e.g. coeliac disease, sprue
Vitamin K-antagonist therapy e.g. anticoagulation with coumarin

Question 9

Inhibition of coagulation:

Answer 9

Specific inhibitors e.g. antibodies against components of factor VIII
Non-specific inhibitors e.g. autoantibodies associated with SLE and RA

Question 10

Miscellaneous Coag disorders

Answer 10

Diseases with paraproteinaemia;
L-asparginase;
Therapy with heparin, defibrinating agents or thrombolytic drugs Massive transfusion syndrome

Question 11

Von Willebrands

Answer 11

.People with VWD have a low level of a substance called von Willebrand factor

The main symptoms are:

bruising easily or getting large bruises
frequent or long-lasting nosebleeds
bleeding gums
heavy or long-lasting bleeding from cuts
in women, heavy periods and bleeding during or after labour
heavy or long-lasting bleeding after a tooth removal or surgery

on Willebrand Factor’s primary function is binding to other proteins, in particular factor VIII, and it is important in platelet adhesion to wound sites.[5] It is not an enzyme and, thus, has no catalytic activity.

Question 12

Long APPT time

Answer 12

A deficiency or inhibition of one or more of the coagulation factors: XII, XI, VIII, X, V, II or I.

1. Haemophilia A
2. Haemophilia B
3. Conditions above

Question 13

Long PT Time

Answer 13

A deficiency or inhibition of one or more of the coagulation factors: VII,X,V,II or I

Question 14

Long TT

Answer 14

1. Deficiency or abnormality of fibrinogen
2. Inhibition of thrombin by heparin or FDP’s

Disorder of the common pathway

Question 15

Antibody Identification Practical

Answer 15

Red cells at the top of, or spread through the gel = positive reaction
Red cells at the bottom of the well = negative reaction

Question 16

Warfarin

Answer 16

The chart above show that Warfarin interferes with the vitamin K cycle. It interacts with the reductase enzyme which means that oxidised vitamin K cannot be converted back to vitamin K. This in turn means, as shown above, that the amount of reduced vitamin K will also decrease. The carboxylation of Precursor Prothrombin (Factor II) to Biologically active Prothrombin requires reduced vitamin K. Hence if the amount of reduced vitamin K is decreased this means that biologically active Prothrombin will not be formed and hence the clotting pathway will be interrupted therefore leading to a reduction in blood coagulation.

Vitamin K is vital for the formation of the clotting factors II, VII, IX and X. As well as the anticoagulant proteins C and S.

Question 17

Heparin

Answer 17

It can be seen how the inhibition of the Factors II (Prothrombin), VII, IX and X have an effect on the formation of a stable fibrin clot. The inhibition of Factor VII has a direct effect on the extrinsic pathway. By inhibiting this factor the whole pathway is blocked. Factor IX and X have an effect early on in the intrinsic pathway.Inhibiting Factor X has a double effect on the extrinsic pathway because if there is still some factor VII in the blood stream it will have no factor X to react with. Hence, it is very unlikely that any Xa and V will be formed to carry on the pathway towards the stable fibrin clot. The inhibition of Prothrombin then has an effect on the production of Thrombin and hence the clot as well. Overall the inhibition of these 4 factors has a major effect on the ability of the body to form a stable fibrin clot.

Question 18

Factor 4

Answer 18

Calcium Ions

Question 19

Extrinsic Pathway

Answer 19

Tissue Factor → VIIa affects X → Xa

Question 20

Heparin vs Warfarin

Answer 20

Pregnancy: Heparin No, Warfarin SAFE

Warfarin Antidote FFP, Vit K
Heparin Antidote Protamine Sulphate

Warfarin monitor INR
Heparin monitor APPT

Question 21

Heparin affects

Answer 21

11
9
7
10
2

But the active forms.