1. PT & aPTT PROF.DR. MOHAMMAD SOROUR CONSULTANT HAEMATOLOGY B.C.H.

2. Hemostasis Is a Balance Between Clot Formation & Clot Dissolution.

3. Normal Hemostasis Clot formation (Coagulation) Clot dissolution (Fibrinolysis) PT aPTT Thrombin Time Fibrinogen Individual factor tests FDP D-Dimer vWF HMWK Prekallikrein

11. Coagulation Factors Factor Trivial Name Pathway Prekallikrein Fletcher factor Intrinsic HMWK Contact activation cofactor Intrinsic I Fibrinogen Both II Prothrombin Both III Tissue Factor Extrinsic IV Calcium Both

12. V Proaccelerin, Labile factor Both VI (Va) Accelerin Both VII Proconvertin Extrinsic VIII Antihemophilic factor A Intrinsic XI Antihemophilic factor B Intrinsic

13. XII Hageman Factor Intrinsic XIII Fibrin Stabilizing factor Both

20. Mixing studies in PT PT mixing study (1:1 mix of patient and normal plasma PT normalizes Factor Deficiency; Measure factors I, II, V, VII, X PT initially shortens and then prolongs Factor V inhibitor (rare) aPTT remains prolonged Inhibitor (specific factor inhibitor, rare) Treat specimen with heparinase (degrades heparin) PT normal, prolongation due to heparin PT prolonged

21. Mixing studies in aPTT aPTT mixing study (1:1 mix of patient and normal plasma aPTT normalizes Factor Deficiency; Measure factors VIII, IX, XI, XII aPTT initially shortens and then prolongs Factor VIII inhibitor aPTT remains prolonged Inhibitor, most commonly Lupus Anticoagulant Treat specimen with heparinase (degrades heparin) aPTT normal, prolongation due to heparin aPTT prolonged