To find Blood clotting time for a given subject:
Introduction:
Clotting time (CT) is the time interval from oozing of blood after a cut or injury till the formation of clot. It is usually determined by capillary tube method. Clotting time is the interval between the moment when bleeding starts and the moment when the fibrin thread is first seen.
Normal value
is 3to 10 minutes. In order for blood to clot, the enzyme thrombin must be generated from the plasma precursor prothrombin. Thrombin then converts soluble fibrinogen into insoluble fibrin. Generation of thrombin involves the sequential activation of a number of other plasma clotting factor, this process is also being assisted by Ca
++
and by factors released by platelets and damaged tissues . The time taken for blood to clot mainly reflects the time required for the generation of thrombin in this manner. If the plasma concentration of prothrombin or of some of the other factors is low (or if the factor is absent, or functionally inactive), clotting time will be prolonged.
Bleeding time and clotting time are not the same. Bleeding time depends on the integrity of platelets and vessel walls, whereas clotting time depends on the availability of coagulation factors. In coagulation disorders like haemophilia, clotting time is prolonged but bleeding time remains normal.
Clotting time is also prolonged in conditions like vitamin K deficiency, liver diseases, disseminated intravascular coagulation, over dosage of anticoagulants etc.
Requirements:
Subject, cotton Alcohol, Lancet, Filter paper and capillary tubes.
Procedure:
1. Wash your hands properly with soap and allow it to dry.
2. Clean your finger with alcohol swab.
3. Prick the finger and make a big drop of blood.
4. Collect the blood in a capillary tube until it fill.
5. Start the stop watch.
6. Break small pieces of capillary tube after each one minute till the fibers are formed.
7. Note down the reading.
Precautions:
1. Lancet should be sterilized
2. Don’t prick to deep.
3. Clean the laboratory after performing pratical procedure.
Observation: The subject clotting time was found 180 secs
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