coagulation time

7/30/2019 Coagulation Time

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Coagulation Time of

whole blood


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Coagulation Time ( Clotting Time) CT.

Clotting time was used as a screening test to measure allstages in the intrinsic coagulation system and to monitorheparin therapy .

It is however, a time-consuming test, has poorreproducibility, is sensitive only extreme factordeficiencies, and is insensitive to high doses of heparin. Itis therefore, of limited use in todays laboratory .

Severe hemophilia, a fibrinogenemia, and severfibrinolytic states cause a prolonged clotting time, as docirculating anticoagulants ( inhibitors), and heparin.


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The normal range for the testdescribed below is 5 to 15 min. buteach laboratory should determine itsown normal values.

Reagent & equipment1.Water bath, 37C.2.Glass test tube.3.Stopwatch.4.Plastic syringe and 20-gauge needle.


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Specimen

Fresh whole blood , 4 ml .

PrincipleThe coagulation time of whole blood is

the length of time required for a

measured amount of blood to clotunder certain specified conditions.


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Procedure

1. Label 3 glass test tube with patient nameand number them, #1, #2, and #3.

2. Perform a clean, unromanticvenipuncture 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.


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Procedure

4. Place the three test tubes in a 37C water bath.

5. At exactly 5 min., title test tube #1 gently to a45 angle. Repeat this procedure every 30

seconds, until the test tube can be completelyinverted without spilling the contents (that is,until the blood is completely clotted).

6. Record the time it took the blood in test tube #1to clot.


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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 30seconds, until a clot is formed.Record the results. Repeat thisprocedure for test tube #3.

8. Since agitation and handling speedup coagulation, the clotting timetest tube #3 is the reported result.


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Discussion1. 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 sampleis being obtained increase the rate of coagulation.

Unnecessary agitation of the blood shortens thecoagulation time.

3. Always tilt the tube in the same direction and at thesame angle so that the blood is moving in the samepathway up the side of the tube each time.

4. At the completion of the clotting time, one tubeshould remain in the 37C water bath to be checked

after 2 and 4 hours for clot retraction. Also, thissame tube may be allowed to remain in the waterbath overnight and checked the next day for clotlysis.


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Clotting time - capillary method(Extrinsic)

Apparatus :

1. Sterile disposable pricking needle or lancet.

2. Stop watch3.Dry glass capillary tube (narrow diameter 1 top 2

mm, minimum 10 cm long.)

4. Cotton Swab of absorbent cotton.

5.Spirit wetted, cotton swab.

6. 70 % v/v ethyl alcohol


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PROCEDURE1. 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. Immediately

stop watch is started.3. Dip one end of the capillary into blood drop gently without

pressure.4. Allow to fill the capillary with blood by lowering the end offitted capillary. (Do not suck the blood) around th of itslength undipped.

5. After every 30 seconds, using stopwatch, break a smallpiece of capillary.

6. Repeat breaking at regular time intervals, till fibrin threadappears at the broken end of capillary tube. Do not pullaway the cut pieces ling apart and bristly.

7. Record time interval between pricking finger and firstappearance of fibrin thread at the broken ends of capillarytube. That is clotting time of blood.


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Clotting time of whole blood


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Clotting Time - Slide Method(Intrinsic)

The surface of the glass tubeinitiates the clotting process.This test is sensitive to thefactors involved in theintrinsic pathway

The expected range for

clotting time is 4-10 min.


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Clot retraction

This test measures the amount of time it takes

for a blood clot to pull away from the walls of

a test tube.

It is used to evaluate and manage blood

platelet disorders, including Glanzmann's

thrombasthenia


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Glanzmann's thrombasthenia

Is an abnormality of theplatelets

It is an extremely rare coagulopathy in whichtheplateletslackglycoprotein IIb/IIIa .

Hence, no fibrinogen bridging can occur, and

bleeding time is significantly prolonged.


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Clot retraction test

This is a measure of platelet function. The test is donein blood to which no anticoagulant has been addedand is allowed to clot. Clot retraction is then looked

for.

Clot retraction becomes abnormal in conditions like

Fibrinogen deficiency (congenital or acquired)

Thrombocytopenia < 1oooooThrombosthenia

Polycythaemia


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Procedrure

1. At the completion of the

clotting time one tube

should remain in the 37

water bath

2. Inspect the clot at 1,2,4

and 24 hr for retracted clot


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Interpretation of results

The clot will retract from the walls of thetube until the red cell mass occupies 50%of the total volume of blood in the tube

There is a variable degree of retraction orthere is no retraction at all

Results are reported as the length of timeit took for the clot to retract

2-4 hrs is reported as normal After 4 hrs is reported as poor

After 24 hrs is reported as no retraction


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The whole blood clot lysis time is used to detect

increase fibrinolysis This test is only able to detect high increase in

fibrinolytic activity

Clot lysis test


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Procedure

1. At the completion of the clotting time one tubeshould remain in the 37 water bath

2. A second tube is placed in the refrigerator as soonas clotted as a control

3. The tube is test for the disappearance of clot after4, 8 and 24 hrs

4. If the sample becomes fluid in less than 48 hrs ,the blood is poured out onto a piece of filter paperto be sure for clot disappearance


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Interpretation

The disappearance of clot before 48 hrs meansincrease fibrinolysis

After 48 hrs clot may be

CommentRefrigerated tube37 C tube

Low fibrinogendisappeardisappear

Abnormalfibrinolysis

(No clot lsis after 48 hrs)

Still intactStill intact

Nomal fibrinolysisStill intactdisappear

coagulation time

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