Clotting Time (C T)

Sample

• Clotting Time is done on a fresh sample of blood and the patient needed to be in the lab.

Indications

1. Clotting Time is advised to find bleeding disorder, most likely due to clotting factors deficiency.
2. To Diagnose hemophilia.

Precaution

• It does not diagnose mild coagulation disorders.

Pathophysiology

1. For the clot formation prothrombin is converted into thrombin.
2. Thrombin converts soluble fibrinogen into insoluble fibrin.
3. For this process clotting factors are needed along with calcium.
4. Also assisted by the factors produced by platelets and damaged tissue.
5. So clotting time is the time needed for the generation of thrombin from the complex system of clotting.

6. When there is any deficiency in these factors, it will lead to prolonged clotting time.
7. Now, it is rarely used because of the variation, instead, the clotting factors are more accurate.

Procedure

1. Clotting time can be estimated by two methods:
   1. Capillary method.
   2. Test tube method.
      1. Perform this test at 37 ° C.
      2. For the tube, the method takes 4 ml of blood and start the time.
         1. Note the time when there is the first appearance of the clot formation.
      3. This test can be done in multiple tubes to be more accurate.

Normal

• The expected range is 4 to 10 minutes.
• The glass tube method clotting time is 5 to 15 minutes.
• Siliconized tubes clotting time is 19 to 60 minutes.

Causes of prolonged clotting time are:

1. Coagulation factors deficiencies which may be:
   1. Congenital.
   2. Acquired.
2. Drugs like heparin and thrombin inhibitor.

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