Lecture 12 - Coagulation in the Lab and Bleeding Disorders

Question 1

APTT test?

Answer 1

test of intrinsic pathway, includes all factors except VII, exclusive for XII XI IX and VIII

Question 2

APTT process?

Answer 2

venous sample collected, added to citrate to deactivate clotting through calcium removal, spin to separate for plasma, add phospholipid and activator, add calcium, time clot formation

Question 3

PR Test?

Answer 3

extrinsic pathway, prothrombin time, VII X prothrombin, fibrinogen, prothrombin time converted to ratio

Question 4

Thrombin clotting time?

Answer 4

adding activated thrombin to assay meaning no requirement or previous pathwyas

Question 5

Mixing Studies?

Answer 5

1:1 mixing with nomal plasma, sample correction to normal indicates factor deficiency, no full correction means inhibitor prescence

Question 6

Natural inhibitors?

Answer 6

antithrombin, protein C and S, shut down coagulation, do not effect APTT

Question 7

Lupus anticoagulant?

Answer 7

prolongs APTT, antibody interference possibly part of antiphospholipid syndrome, transient presence in unwell patients, doesnt cause bleeding

Question 8

Factor inhibitors?

Answer 8

prolongs APTT, autoimmune antibodies against clotting factor (usually VIII), bleeding association (bruising), potentially life threatening, rare but should be considered in bleeding patient

Question 9

Heparin?

Answer 9

drug itself at high testing dose prolongs APTT, comfirm with protamine addition, biologically inhibits via upregulating antithrombin by increases GAGs (does not affect APTT biologically)

Question 10

Heparin contamination?

Answer 10

common in tube collection via lock central lines that use heparin as anticoagulant

Question 11

Dabigatran?

Answer 11

direct inhibitor of thrombin, prolonged APPT 1+1 not corrected with protamine,

Question 12

APTT prolonged, PT normal?

Answer 12

deficiencies of factors VIII, IX, XI, XII (intrinsic)

Question 13

PT prolonged, APTT normal?

Answer 13

deficiency of VII (extrinsic), occasionally mild deficiencies of II, V, X, I

Question 14

Both PT and APTT prolonged?

Answer 14

deficiency of factors II, V, X and I (common), multiple factor deficiencies

Question 15

TCT prolonged?

Answer 15

deficiency of fibrinogen, thrombin inhibitor (dabigatrin or heparin)

Question 16

Multiple factor deficiencies?

Answer 16

warfarin or vitamin K deficiencies (II, VII, IX, X), massive blood loss, DIsseminated Intravascular Coagulation (activation of coagulation cuasing thrombois followed by bleeding as factors and platelets are used up, low fibrinogen), liver disease (lack of production except VIII)

Question 17

Warfarin mechanism of action?

Answer 17

inhibits recycling of vitamin K, dose adjustments via international normal ratio (INR), reversed by vitamin K or rapid replacement of clotting factors

Question 18

Warfarin used for?

Answer 18

atrial fibrillation, venous thromboembolism, other thrombotic disorders

Question 19

Haemophilia A?

Answer 19

factor VIII deficiency, 1 in 5000 live male births

Question 20

Haemophilia B?

Answer 20

deficiency of factor XI, x-linked recessive inheritance, more rare, identical clinically to A

Question 21

Treating haemophilia?

Answer 21

replace missing factor, treating prophylaxis of severe conditions, outcomes good unless inhibitors develop

Question 22

Von Willebrand Factor?

Answer 22

plasma glycoprotien, synthesised in megakaryocytes and endothelial cells, promotes platelet adhesion at vessel wall, carrier for Factor VIII

Question 23

Symptoms of van Willebrand disease?

Answer 23

mucosal bleeding, bruising, menorrhagia, autosomal family history