Coagulation Time Tube Method Mr. Mohammed A. Jaber

Coagulation Time ( Clotting Time) CT. Clotting time was used as a screening test to measure all stages in the intrinsic coagulation system and to monitor heparin therapy. It is however, a time-consuming test, has poor reproducibility, is sensitive only extreme factor deficiencies, and is insensitive to high doses of heparin. It is therefore, of limited use in today’s laboratory.severe hemophilia, a fibrinogenemia, and sever fibrinolytic states cause a prolonged clotting time, as do circulating anticoagulants ( inhibitors), and heparin.

The normal range for the test described below is 5 to 15 min. but each laboratory should determine its own normal values. Reagent & equipment 1.Water bath, 37C. 2.Glass test tube. 3.Stopwatch. 4.Plastic syringe and 20-gauge needle.

Spacemen Fresh whole blood, 4 ml. Principle The coagulation time of whole blood is the length of time required for a measured amount of blood to clot under certain specified conditions.

Procedure 1.Label 3 glass test tube with patient name and number them, #1, #2, and #3. 2.Perform a clean, unromantic venipuncture using a 20-gauge needle and with drawn 4 mL of blood. 3.Remove the needle from the syringe, and carefully place 1 mL of blood in test tube #3, 1mL in tube #2, and 1mL in tube #1. the last 1 mL of blood may be discarded. Start the stopwatch as soon as the blood is placed in tube #3.

Procedure 4.Place the three test tubes in a 37°C water bath. 5.At exactly 5 min., title test tube #1 gently to a 45° angle. Repeat this procedure every 30 seconds, until the test tube can be completely inverted without spilling the contents (that is, until the blood is completely clotted). 6.Record the time it took the blood in test tube #1 to clot.

Procedure 7.30 sec. after the blood in test tube #1 is clotted. Proceed with tube #2, and repeat the preceding procedure, tilting the test tube every 30 seconds, until a clot is formed. Record the results. Repeat this procedure for test tube #3. 8.Since agitation and handling speed up coagulation, the clotting time test tube #3 is the reported result.

Discussion 1.Poor venipuncture technique, causing hemolysis or tissue thromboplastin to mix with the blood, shortens the clotting time. 2.Bubbles entering the syringe when the blood sample is being obtained increase the rate of coagulation. Unnecessary agitation of the blood shortens the coagulation time. 3.Always tilt the tube in the same direction and at the same angle so that the blood is moving in the same pathway up the side of the tube each time. 4.At the completion of the clotting time, one tube should remain in the 37°C water bath to be checked after 2 and 4 hours for clot retraction. Also, this same tube may be allowed to remain in the water bath overnight and checked the next day for clot lysis.