Tabuk University

1. Tabuk University Faculty of Applied Medical Sciences Department Of Medical Lab. Technology 3rd Year – Level 5 – AY 1434-1435 Hematology – 2, MLT 307

2. Thrombotic disorders By/ Dr. Walid ZAMMITI; Phd M.Sc; MLT

3. Objectives • Define terms used in thrombotic disorders. • Identify the most common causes for thrombosis. • Classify thrombosis into arterial and venous; and the differences between them. • Classify thrombotic disorders into hereditary and acquired. • Understand the mechanism of thrombosis in specific hereditary & acquired conditions. • Learn the diagnostic tests used to identify genetic predisposition to thrombosis.

4. Disease processes Abnormal clotting Abnormal bleeding Bleeding disorders : caused by Platelets, vascular, coagulation factors Thrombotic disorders

5. Thrombosis • Thrombus: singular , Thrombi : Plural • Thrombi are solid masses or plugs formed in the circulation from blood constituents. • Platelets and fibrin form the basic structure. Their clinical significance results from ischaemiafrom local vascular obstruction or distant embolization. • Thrombi are involved in the pathogenesis of myocardial infarction, cerebrovascular disease, peripheral arterial disease and deep vein occlusion.

7. Thrombosis may be arterial, causing ischemia, or venous leading to stasis. • Thrombosis, both arterial and venous, is more common as age increases and is frequently associated with risk factors. The term thrombophiliais used to describe the inherited or acquired disorders of the haemostaticmechanism that predispose to thrombosis.

8. Arterial thrombosis • Atherosclerosis تصلب الشرايينof the arterial wall, plaque rupture and endothelial injury expose blood to subendothelialcollagen and tissue factor. This initiates the formation of a platelet plugs on which platelets adhere and aggregate.

9. Venous thrombosis • It is suggested that there are threecomponents that are important in thrombus formation: 1. Slowing down of blood flow; 2 .Hypercoagulability of the blood; and 3 .Vessel wall damage. • Increased systemic coagulabilityand stasis are most important, vessel wall damage being less important than in arterial thrombosis

10. Thrombotic disorders • Hereditary -Factor V Leiden gene mutation (activated protein C resistance) • Antithrombin deficiency • Protein C deficiency • Protein S deficiency • Prothrombin allele G20210A • Hyperhomocyst(e)inaemia • Defects of fibrinogen • Acquired • Post surgery • Post delivery • Long distance travel • Immobilization • Malignancy • Inflammation • Blood disorders • Oestrogentherapy • The antiphospholipidsyndrome • Factor IX concentrates

11. Activated Protein C (APC) Resistance(Factor V Leiden mutation) • Genetic alterations of the factor V molecule at APC binding sites impair, or resist APC’s ability to degrade or inactivate factor Va. • Site of mutation is replacement of arginine at position 506 with glutamine (Arg506Gln) in the factor V gene. • It is the most common inherited cause of increased risk of venousthrombosis. • It doesn’t increase risk of arterial thrombosis • Diagnosed by PCR : Polymerase Chain Reaction.

12. Antithrombin III ATIII inhibits thrombin to prevent thrombus formation Fibrinogen “Thrombus” Fibrin Antithrombin • Also known as Antithrombin III • Antithrombin forms "complexes" with all the serine protease coagulation factors except factor VII, this "kills" the enzyme. Thrombin Prothrombin

13. Antithrombin deficiency • There are recurrent venous thromboses usually starting in early adult life. Arterial thrombi occur occasionally.

14. Protein C & S

16. Protein C andProtein C Deficiency • Protein C is a vitamin K dependent glycoprotein produced in the liver • In the activation of protein C, thrombin binds to thrombomodulin, a structural protein on the endothelial cell surface • This complex then converts protein C to activated protein C (APC), which degrades factors Va and VIIIa, limiting thrombin production • For protein C to bind, cleave and degrade factors Va and VIIIa, protein S must be available • Protein C deficiency, whether inherited or acquired, may cause thrombosis when levels drop to 50% or below • Protein C deficiency occurs with surgery, trauma, pregnancy, liver or renal failure or DIC.

17. Protein S, Protein S Deficiency • Protein S is an essential cofactorin the protein C pathway • Protein S exists in a free and bound state • About 30% of unbound protein S, called free PS, is the functionally active form of protein S • Inherited PS deficiency is an autosomal dominant disorder, causing thrombosis when levels drop to 50% or lower

18. Causes of Acquired Protein S Deficiency Decreased PS Functional activity may be due to : • vitamin K deficiency • liver disease • Due to increased PS consumption which occurs in acute thrombosis, DIC, MPD, sickle cell disease

19. Prothrombin gene mutation • Prothrombin allele G20210A is a variant (prevalence 2-3% in the population) that leads to increasedplasma prothrombin levels and increases thrombotic risk by at least twofold.

20. Acquired risk factors of thrombosis

21. - Post surgery: elderly, obese & those with family history. • - Venous stasis and Immobilization : probably responsible for the high • incidence of postoperative venous thrombosis. • Malignancy : carcinoma of the ovary, brain and pancreas have a particularly increased risk of venous thrombosis but there is an increased risk with all cancers. • Inflammation : down regulates anticoagulant pathways, particularly proteinC. • - Blood disorders :In polycythaemiavera and essential thrombocythaemia; there are Increased viscosity, thrombocytosis, altered platelet membrane receptors and responses.

22. Antiphospolipid syndrome • Def: occurrence of thrombosis or miscarriage in association with antiphspholipid antibodies. * Antiphospholipid antibodies may be: • Lupus anticoagulant (LA); causing prolonged APTT not corrected by mixing with normal plasma. • Anticardiolipin antibodies (ACA).

23. AntiphospholipidSyndrome :Diagnosis • Clinical association of (APA): -Arterial or venous thrombosis -Pregnancy loss -Thrombocytopenia -CNS stroke • Laboratory Criteria -IgG or IgManticardiolipin antibody-medium or high titer. -Detected in an ELISA assay

24. Oestrogen therapy • Oestrogen therapy, particularly high-dose therapy, is associated with Increased plasma levels of factors II, VII, VIII, IX and X and, • Depressed levels of antithrombin and tissue plasminogen activator in the vessel wall.

25. Investigation of thrombophilia • Screening tests: • Blood count and erythrocyte sedimentation rate (ESR) • Blood film examination - Prothrombintime (PT) and APTT : (a shortened APPT is often seen in thrombotic states and may indicate the presence of activated clotting factors. A prolonged APTT test, not corrected by the addition of normal plasma, suggests a 'lupus anticoagulant‘ or an acquired inhibitor to a coagulation factor.) • Anticardiolipin and anti-β2-GPI antibodies - Thrombin time and reptilasetime: (prolongation suggests an abnormal fibrinogen)

26. Fibrinogen assay. - Activated protein C (APC) resistance test and DNA analysis for factor V Leiden. • Antithrombin-immunological and functional assays. - Protein C and protein S-immunological and functional assays. - Prothrombin gene analysis for the G20210A variant. - Plasma homocysteine estimation - Test for CD59 and CD55 expression (PNH) in red cells. (if paroxysmalnocturnalhaemoglobinuria is suspected.)

27. Anticoagulant drugs • Anticoagulant drugs are used widely in the treatment of venous thromboembolic disease. Their value in the treatment of arterial thrombosis is less well established. • Heparin: laboratory controlled using APTT mainly. • Oral anticoagulants : e.g : Warfarin, laboratory controlled using PT & INR (International Normalized Ratio).

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