QS Study

Clotting time (CT)

Definition: Time required for coagulation of blood. It is affected by calcium ion levels and many diseases. It is performed to detect Coagulation Disorder, Epistaxis and Platelet Disorder and also during the treatment and after the treatment of Excessive Wound Bleeding.

Normal value: 6 to 10 minutes. For the measurement of clotting time by test tube method, blood is placed in a glass test tube and kept at 37° C. The required time is measured for the blood to clot.

Method of determination

(i) Lee & white method: 5 -11 min. Here venous blood is collected in 8 mm diameter glass tube, rocked in a water bath at 37°C & time is noted from the time of venepuncture fill the blood stops flowing.

(ii) Capillary tube method: 2 – 4 min. Here the blood is collected in the capillary tube & total time is noted to form FIBRIN THREADS on breaking tube every 30 seconds.

Importance: In Haemophilia, CT is prolonged. This simple test has been used to diagnose hemophilia, but it does not detect mild coagulation disorders. Its chief application is in monitoring anticoagulant therapy. It is rarely used in clinical practice. Abnormalities in clotting times can be the result of decreased quantity or function of the coagulation factors involved.