General Approach of Haemostasis

1. General Approach of Haemostasis Lecture 3: Coagulation Time of whole blood

2. Coagulation Time ( Clotting Time) CT. Clotting Time is the time required for blood to form a clot in vitro. The basis for the test is that whole blood will form a solid clot when exposed to a foreign surface such as a glass tube. It is a rough measure of all intrinsic clotting factors in the absence of tissue factors. Variations are wide and the test sensitivity is limited. As the test is the least effective test in the diagnosis of actual haemostasis failure, it has been replaced by PTT. Clotting time was used as a screening test to measure all stages in the intrinsic coagulation system and to monitor heparin therapy . Clotting is the formation of a jelly like substance over the valves of the vessels. Clotting is the formation of a jelly like substance over the valves of the vessels.

3. It is however, a time-consuming test, has poor reproducibility, is sensitive only extreme factor deficiencies. It is therefore, of limited use in today’s laboratory . It is a complex process involving over 30 substances Conditions accompanied by increased Clotting Time: Factors V, VII, VIII, IX, XI, XII Deficiencies. Hemorrhagic disease of Newborn Vitamin K deficiency. Heparin Therapy. Presence of Circulating antibodies (inhibitors) Anemia and leukemia. Afibinogenemia and Pneumonia. and heparin. Reproducibility is the ability of an experiment or study to be accurately reproduced, or replicated, by someone else working independently. It is one of the main principles of the scientific method. Heparin: Works by markedly enhancing activity of antithrombin, which inhibits activated factors II, IX, X, XI, XII, kallikrein and probably VII, but doesn’t cause a true decrease in factor levels Vitamin K: prothrombin (factor II), factors VII, IX, X, protein C, protein S, and protein ZReproducibility is the ability of an experiment or study to be accurately reproduced, or replicated, by someone else working independently. It is one of the main principles of the scientific method. Heparin: Works by markedly enhancing activity of antithrombin, which inhibits activated factors II, IX, X, XI, XII, kallikrein and probably VII, but doesn’t cause a true decrease in factor levels Vitamin K: prothrombin (factor II), factors VII, IX, X, protein C, protein S, and protein Z

4. Methods: Capillary Method. Slide Method. Tube Method.

5. Reagent & equipment Water bath, 37O C. Glass test tube (10 x 75 mm) Stopwatch. Plastic syringe and 20-gauge needle. Specimen Fresh whole blood , 4 ml .