Bleeding Time Test in Medical Labortory and full guidance for a Lab Technologist.
BLEEDING TIME (BT)
Principle :
When a standard incision is made on the volar surface of the forearm all mechanisms involved in arrest of bleeding are activated and after some time flow of blood stops. The time taken for the blood to stop flowing, without assistance, from the wound is known as the bleeding time. Bleeding time depends upon the number and function of platelets. If the number of the platelets is reduced below a critical level or these are functionally abnormal, the bleeding time is prolonged.
Requirements
• Lancet or template
• Circular filter paper
• Stopwatch
Duke’s method
In this method incisions are made in the ear lobe, pulp of the finger or heel (while it is warm), as these are the sites rich in capillaries.
• Clean the site with a spirit swab.
• Allow the area to dry.
• With the help of a lancet, puncture deeply so that blood flows out freely. Start the stopwatch. At half min intervals blot the drop of the blood at the site of puncture with the help of a filter paper.
• Keep on doing so until blood stops coming out and there is no mark of blood left on the filter paper. At this point stop the stopwatch and note the time. This is the bleeding time.
Interpretation
Prolongation of BT commonly occurs in:
1. • Thrombocytopenia
2. • Platelet function defects
3. • Aspirin ingestion
4. • Afibrinogenaemia
Shortened bleeding time commonly occurs when the technique is faulty.