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Coagulation Screening And Corrections Practical

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Haemostasis: Coagulation Screening & Corrections Practical
Introduction (10 marks)
• Introduce utility of coagulation
• Theory behind the tests
• Clinical relevance of the tests
Coagulation tests measure functions that are related with clotting, coagulation consists of drawing blood and observing it clot. Chelating out the calcium and beginning the clot in a controlled environment. Coagulation tests used to find out if an individual has a clotting disorders and to measure the various proteins and how they function. There are many conditions that can causes problems with coagulation for example thrombophilia and haemophilia. (TRANSFUSION MEDICINE AND HEMOSTASIS BOOK) The parts in bold are the initiation sites of coagulation.
Activated partial thromboplastin time (APTT) measures the intrinsic pathway of coagulation, which is the generation of fibrin, kaolin activates Factor XII, without activating factor VII. Factor XII converted to XIIa, factor VIIa converts factor XI to XIa, factor XIa converts X to Xa with the help of calcium ions and factor VIIIa, factor Xa then activates the common pathway of coagulation. Platelet factors are needed so the coagulation pathway functions normally. APTT is a good screening test for those with inherited or acquired factor deficiencies. For example some examples of inherited disorders are classic haemophilia A which is a factor VIII deficiency, haemophilia B which is a factor IX deficiency. These diseases causes a prolonged APTT.

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