Coagulation of blood - Clotting Time - Introduction - Methods - Capillary Method - Tube Method - Lee White Method - Procedure - Normal Range - Discussion.

1. PRESENTED BY,
S.SHRUTHI
Dr.NGP ARTS AND SCIENCE COLLEGE

2.  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actual haemostasis failure, it has been replaced by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

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.
 Afibrinogenemia and Pneumonia.
 and heparin.

4.  Capillary 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 .
TUBE METHOD (LEE-WHITE
METHOD(

6. 1.Label 3 glass test tube with patient
name and number them, 1, 2, and 3.
2.Perform a clean, Untraumatic
venupucture using a 20-gauge needle
and drawn 4 mL of blood.
3. Remove the needle from the syringe,
and fill each of the three tubes
with 1 ml blood.
 The last 1 ml of blood may be
discarded.
 Start the stopwatch as soon as the
blood enters the syringe.

7. 4. Place the three test tubes in a 37°C water
bath.
5. At exactly 3 min., Remove the first tube form
water bath and tilt gently to a 45° angle to
see whether the blood has clotted.
6. If Blood not clotted return it to the water
bath and examine it at 30 second intervals.
7. After the blood in the first tube has clotted,
examine the second tube immediately.
8. Then examine the 3rd
one.
9. Record the time it took the blood in the 3rd
test tube to clot.

8. Normal RangeNormal Range::
55––1212MinutesMinutes

9. 1. Poor venipucture 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.
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. Excessive agitation of blood (occur during the transfer of
the blood from the syringe to the test tube). The blood
should be allowed to flow gently down the inside of the
test tube and not forcefully squirted into the test tube.

10. 5. At the completion of the clotting time, one tube should
remain in the 37°C water bath to be checked 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.
6. Dirty Test Tubes will affect the result.
 Coagulation will be retarded by the following:
 Temperature Below 35O
C.
 Temperature above 45O
C.
 Diameter of the test tube (the smaller the diameter, the
more rapid the clot formation is).

11. Material Required:
 Sterile disposable pricking needle or lancet.
 Stop watch
 Dry glass capillary tube (narrow diameter top 2
mm, minimum 10 cm long.)
 Cotton Swab of absorbent cotton.
 Spirit wetted, cotton swab.
 70 % v/v ethyl alcohol

12. 1. Apply alcoholic 70 % v/v to the clean finger with
cotton swab. Allow it to dry naturally.
2. Prick the finger with usual aseptic precautions.
Remove the first drop.
3. Dip one end of the capillary into blood drop gently
without pressure. (use 3-4 capillary tubes)
4. The Timer is started when the first blood start to enter
the first capillary tube.
5. Allow to fill the capillary with blood by lowering the
end of fitted capillary. (Do not suck the blood)
around ¾th of its length undipped.

13. 6. After every 30 seconds, using stopwatch,
break a small piece of capillary.
7. Repeat breaking at regular time intervals, till
fibrin thread appears at the broken end of
capillary tube. Do not pull away the cut
pieces ling apart and bristly.
8. Record time interval between pricking
finger and first appearance of fibrin thread
at the broken ends of capillary tube. That is
clotting time of blood.
9. Don't forget to dispose of the broken tube in
the SHARPS CONTAINER.