Bleeding Time and Clotting Time

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Introduction:
For the investigation of a case of bleeding disorder,clinical history is very important. An accurate clinical and family history will often give an important time-saving clue to the nature of underlying bleeding disorder.
􀂄 Appearance of purpuric spots or bruises over minimally injured surface suggests an abnormality of
the vascular wall.
􀂄 Continuous bleeding from mucous membranes, cuts, wounds, deeper haematomas or bleeding into the joints will suggest a defect in the blood coagulation
system.
􀂄 Excessive bleeding following delivery, or retention of dead foetus, or oozing following extensive surgery, suggest the possibility of fibrinogen depletion or presence of circulating anticoagulant agents.
􀂄 History should also be taken about the ingestion of antiplatelet drugs such as aspirin.


Two of the commonly used screening tests, bleeding time and whole blood clotting time, are discussed below.


BLEEDING TIME  (BT)
Bleeding time is duration of bleeding from a standard puncture wound on the skin which is a measure of the function of the platelets as well as integrity of the vessel wall. 
This is one of the most important preliminary indicators for detection of bleeding disorders. 
This is also the most commonly done preoperative investigation in patients scheduled for surgery.

Principle
A small puncture is made on the skin and the time for which it bleeds is noted. Bleeding stops when platelet plug forms and breach in the vessel wall has sealed.

Methods for Bleeding Time
1. Finger tip method
2. Duke’s method
3. Ivy’s method

Finger Tip Method

Procedure
􀂄 Clean the tip of a finger with spirit.
􀂄 Prick with a disposable needle or lancet.
􀂄 Start the stop-watch immediately.
􀂄 Start gently touching the pricked finger with a filter paper till blood spots continue to be made on the
filter paper.
􀂄 Stop the watch when no more blood spot comes on the filter paper and note the time.

Disadvantages
i. It is a crude method.
ii. Bleeding time is low by this method.

Normal bleeding time 1-3 minutes.

 Duke’s Method

Procedure

􀂄 Clean the lobe of a ear with a spirit swab.
􀂄 Using a disposable lancet/needle, puncture the lower edge of the ear lobe to a depth of approximately 3 mm.
􀂄 Start the stop-watch immediately.
􀂄 Allow the drops of blood to fall on a filter paper without touching the ear lobe and then slowly touching the blood drop gently on a new area on the filter paper.
􀂄 Stop the watch when no more blood comes over the filter paper and note the time.

Advantages of the method
i. The ear lobule has abundant subcutaneous tissue and is vascular.
ii. Flow of blood is quite good.

Normal bleeding time 3-5 minutes

Ivy’s Method

Procedure
􀂄 Tie the BP apparatus cuff around the patient’s upper arm and inflate it upto 40 mmHg which is maintained throughout the test.
􀂄 Clean an area with spirit over the flexor surface of forearm and let it dry.
􀂄 Using a disposable lancet or surgical blade make 2 punctures 3 mm deep 5-10 cm from each other
taking care not to puncture the superficial veins.
􀂄 Start the stop-watch immediately.
􀂄 Go on blotting each puncture with a filter paper as in Duke’s method.
􀂄 Stop the watch, note the time in each puncture and
calculate average bleeding time.

Advantages of the method
i. This is the method of choice.
ii. It is a standardized method.
iii. Bleeding time is more accurate.

Normal bleeding time 3-8 minutes.

Clinical Application of Bleeding Time
The bleeding time is prolonged in:
i. Thrombocytopenia
ii. Disorders of platelet functions
iii. Acute leukaemias
iv. Aplastic anaemias
v. Liver disease
vi. von Willebrand’s disease
vii. DIC
viii. Abnormalilty in the wall of blood vessels
ix. Administration of drugs prior to test e.g. aspirin


CLOTTING TIME  (CT)
This is also known as whole blood clotting time and is a measure of the plasma clotting factors. 
It is a screening test for coagulation disorders.

Various other tests for coagulation disorders include:
Prothrombin time (PT), partial thromboplastin time (PTTK) or activated partial thromboplastin time with
kaolin (APTTK), and measurement of fibrinogen.
Whole Blood Clotting Time
Methods
1. Capillary tube method
2. Lee and White method

1. Capillary Tube Method
Procedure
􀂄 Clean the tip of a finger with spirit.
􀂄 Puncture it upto 3 mm deep with a disposable needle.
􀂄 Start the stop-watch.
􀂄 Fill two capillary tubes with free flowing blood from the puncture after wiping the first drop of blood.
􀂄 Keep these tubes at body temperature.
􀂄 After 2 minutes start breaking the capillary tube at 1 cm distance to see whether a thin fibrin strand is
formed between the two broken ends.
􀂄 Stop the watch and calculate the time from average of the two capillary tubes.

Disadvantages
i. Method is insensitive.
ii. Method is unreliable.
Advantages
Can be performed when venous blood can not be obtained.

Normal clotting time 1-5 mintues.

2. Lee and White Method
Procedure
􀂄 After cleaning the forearm, make a venepuncture and draw 3 ml of blood in a siliconised glass syringe or plastic syringe.
􀂄 Start the stop-watch.
􀂄 Transfer 1 ml of blood each into 3 glass tubes which are kept at 37oC in a waterbath (Fig. 51.2).
􀂄 After 3 minutes tilt the tubes one by one every 30
seconds.
􀂄 The clotting time is taken when the tubes can be tilted without spilling of their contents.
􀂄 Calculate the clotting time by average of 3 tubes.

Advantages
i. More accurate and standard method.
ii. Test can be run with control.
Disadvantages
i. It is also a rough method.
ii. There can be contamination of syringe or tubes.

Normal clotting time 5-10 mintues.

Sources of Error
i. The temperature should be maintained because higher temperature accelerates clotting.
ii. The diameter of the glass tubes should be uniform because clotting is accelerated in narrow tubes.
iii. Vigorous agitation of the tubes should be avoided as it shortens the clotting time.

Clinical Applications
Clotting time is prolonged in:
i. Severe deficiency of coagulation factors.
ii. Afibrinogenaemia.
iii. Administration of heparin.
iv. Disseminated intravascular coagulation (DIC).
v. Administration of drugs such as anticoagulants

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