Five different components are involved in normal hemostasis, namely blood vessels, platelets, plasma coagulation factors, their inhibitors, and the fibrinolytic system. Blood vessels and platelets are the major components involved in primary hemostasis (vascular & platelet phase). Bleeding time is used to screen the abnormalities of this phase.
Principle
A standard incision is made on the volar surface of the forearm, and the time the incision bleeds is measured. Cessation of bleeding indicates the formation of hemostatic plugs, which are in turn dependent on an adequate number of platelets and on the ability of platelets to adhere to the subendothelium and form aggregates.
Method:
Ivy’s method
Equipment & Reagents:
1. Sphygmomanometer
2. Cleansing swab
3. Disposable lancet
4. Filter paper (1 mm thick)
5. Stop-watch
Calibration Procedure:
Steps of Procedure:
- Place a sphygmomanometer cuff around the patient’s arm above the elbow, inflate to 40 mm Hg, and keep it at this pressure throughout the test.
- Clean the area with 70% ethanol and allow to dry. Choose an area of skin on the volar surface of the forearm that is devoid of visible superficial veins.
- Two standard punctures, 5–10 cm apart, are made in quick succession using a disposable lancet. Any microlance with a cutting depth of 2.5 mm and width of just more than 1 mm is suitable.
- With the edge of a filter paper, at 15 second intervals, blot off the blood exuding from the cut.
- Avoid contact with the wound during this procedure because this may disturb the formation of the platelet plug.
- When bleeding has ceased, carefully oppose the edges of the puncture and apply adhesive strip.
Normal range
2 – 7 minutes
Interpretation of Results
A prolonged bleeding time may result from the following:
1. Thrombocytopenia: It is advisable to check the platelet count before carrying out the bleeding time test.
2. Disorders of platelet function.
3. VWD.
4. Vascular abnormalities.
5. Occasionally, severe deficiency of factor V or XI, or afibrinogenaemia.
Interference & Cross Reaction
The bleeding time is subject to a large number of variables and confounding factors. It is important to standardize the sphygmomanometer pressure, longitudinal orientation of the incision, volar aspect of the arm, and the blotting technique. Attempting to repeat the test within a short period of time will usually result in a shorter bleeding time. A normal bleeding time does not imply normal hemostasis, and the result of the test has been shown not to correlate with bleeding at other sites.
Quality Control
Safety Precaution: Every test sample is regarded as potentially infectious material, so universal safety precautions have to be taken.