Estimation of Clotting Time & Bleeding Time

 

Introduction:

Haemostasias :   Blood clotting

Hemostasis or haemostasias is a complex process, which causes the bleeding process to stop. It refers to the process of keeping blood within a damaged blood vessel. Most of the time this includes the changing of blood from a fluid to a solid state. Intact blood vessels are central to moderating blood's tendency to clot.

In order for blood to clot, the enzyme thrombin must be generated from the plasma precursor prothrombin. Thrombin then converts soluble fibrinogen into insoluble fibrin. Generation of thrombin involves the sequential activation of a number of other plasma clotting factor, this process is also being assisted by Ca⁺⁺ and by factors released by platelets and damaged tissues . The time taken for blood to clot mainly reflects the time required for the generation of thrombin in this manner. If the plasma concentration of prothrombin or of some of the other factors is low (or if the factor is absent, or functionally inactive), clotting time will be prolonged. The expected range for clotting time is 4-10 mins.

Coagulation Time

 The time required for a sample of blood  to coagulate in vitro under standard conditions   is called "clotting time" There are various methods for determining this, the most common being capillary tube method. Clotting is the formation of a jelly like substance over the valves of the vessels. The result is stoppage of blood flow. Clotting is one of the natural defense mechanism to prevent blood loss from the body .A clot is usually formed within 5 minutes after injury. Whenever a blood vessel is cut there is a rush of platelets causes a cut or injury 

To be filled and thus bleeding stops. Clotting initiated by two pathways i.e. intrinsic pathway and extrinsic pathway. Clotting time is affected by calcium ion and many   diseases. Normal value of clotting time is 5-8 minutes. Other methods for measuring clotting time are slide method

Method: Capillary method

Normal range: 4 to 9 minutes

Specimen: Capillary blood

 

Principle

Blood is collected in a capillary tube after a finger prick and the stop watch is started . The formation of fibrin string is noted by breaking the capillary tube at regular intervals, the time is noted at the first appearance of the fibrin string.

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Requirements : Sterile lancet, Capillary tube(1.5mm diameter and 10 to 15 cm length),Cotton, Spirit or 70% alcohol, Stopwatch

Procedure

1.      By using a piece of cotton , apply spirit or 70% alcohol to the patient’ finger tip.

2.      Make a deep (1mm) incision with a sterile lancet and start the stop watch.

3.     Wipe of the first drop formed  and collect blood in the capillary up to 2/3 of its length.

4.     After every half minute, break off about 1cm of the capillary to find out whether fibrin string has formed.

5.     When the fibrin string appears, stop the stopwatch and note down the time. 

Bleeding:

Bleeding, technically known as hemorrhaging or hemorrhaging  is the loss of blood or blood escape from the circulatory system. Bleeding can occur internally, where blood leaks from blood vessels inside the body or externally, either through a natural opening such as the vagina, mouth, nose, ear or anus, or through a break in the skin.

This test measures the time taken for blood vessel constriction and platelet plug formation to occur. No clot is allowed to form, so that the arrest of bleeding depends exclusively on blood vessel constriction and platelet action. Normal Range of Platelets for Adults:  150,000-500,000 platelets/mm³

Bleeding time test : Duke Method

Principle :

A 1mm deep incision is made on the earlobe or finger of the patient. The length of time required for bleeding to cease is recorded.

Normal Range: 1-5 minutes

Specimen: Blood collected by ear lobe or finger puncture

Requirements

1)      Sterile Lancet,,Spirit or 70% alcohol,Circular Filter Paper,Stopwatch

Procedure

1.      Clean the ear lobe (or finger) with spirit or alcohol by using apiece of cotton. Allow to dry.

2.      Puncture the ear lobe (or finger) deeply (about1mm) by using sterile lancet. Start the stopwatch. The blood should flow freely, without squeezing the ear lobe(or finger).

3.     After 30 seconds collet the drop of blood at one corner of the paper. Do not touch the skin without paper.

4.     Repeat step no.3 after every 30 seconds.

5.     When bleeding ceases, stop the stopwatch.

6.     Note the time on the watch.

Interpretation

·    Bleeding time is affected by platelet function, certain vascular disorders and von Willebrand Disease

·   Diseases that cause prolonged bleeding time include thrombocytopenia, Bernard-Soulier disease, and Glanzmann's thrombasthenia.

·  Aspirin and other cyclooxygenase inhibitors can prolong bleeding time significantly. While warfarin and heparin have their major effects on coagulation factors, Determination of bleeding time

 

Clinical Significance

Determination of bleeding time helps to detect vascular defect and plate disorder. Prolonged bleeding time is generally associated with thrombocytopenia. In case of von Willebrand’s disease, bleeding time is high with a normal platelet count. It is caused by a platelet defect combined with factor VIII deficiency.

Normal ESR test results

•       ESR test results are measured in millimeters per hour (mm/hr)

•       The following are considered normal ESR test results:

o   Women             under age 50 should have an               ESR between 0 and 20 mm/hr.

o   Men                    under age 50 should have an               ESR between 0 and 15 mm/hr.

o   Women             over age 50 should have an   ESR between 0 and 30 mm/hr.

o   Men                    over age 50 should have an   ESR between 0 and 20 mm/hr.

o   Children             should have an                                           ESR between 0 and 10 mm/hr.