What are other Names for this Test? (Equivalent Terms)
- BT Blood Test
What is Bleeding Time Blood Test? (Background Information)
- Blood clot formation normally starts with injury to a blood vessel, which causes it to constrict. Called the vascular phase, this is the first reaction of a blood vessel to damage. It reduces the flow of blood to the site of injury, minimizing blood loss
- Next, the circulating platelets clump along the site of blood vessel injury. The platelets form a foundation for a blood clot and release chemicals that stimulate clotting
- The coagulation phase then causes a blood clot to form. Clotting occurs when an enzyme called thrombin converts a soluble protein, fibrinogen, into its insoluble form, fibrin. Fibrin proteins make up the bulk of a blood clot
- Thrombin is activated by the merging of two pathways, the intrinsic and extrinsic pathways, into the common pathway. These are initiated by different parts of the body after blood vessel damage:
- The intrinsic pathway begins in blood with the activation of circulating proteins;
- The extrinsic pathway begins in the blood vessel with the release of protein factors by damaged cells lining the vessel
- The extrinsic pathway is the first to activate. The intrinsic pathway then reinforces the extrinsic pathway and provides longer-lasting clotting effects
- Coagulation factors are central to the action of these pathways. Each factor activates the next in a stepwise fashion. Once a coagulation factor is activated, it remains active. Thus, with each step in the pathway, more and more factors are activated. This results in a cascade of events similar to the snowball effect
- A counter pathway ensures that the size of the growing blood clot stays in check. Problems with this regulatory pathway may lead to a dangerous condition where a blood clot forms within blood vessels (thrombosis)
- Vitamin K is necessary for the formation of coagulation factors II, VII, IX, and X. These factors span across all three coagulation pathways. The anticoagulant drug warfarin interferes with the necessary enzymes’ abilities to use vitamin K and make these clotting factors
- The Bleeding Time Blood Test helps determine the coagulation system’s ability to stop bleeding. It is used to diagnose blood disorders
What are the Clinical Indications for performing the Bleeding Time Blood Test?
Following are the clinical indications for performing the Bleeding Time Blood Test:
- Measuring coagulation ability when more sophisticated methods are unavailable
- Monitoring hemostatic therapy
How is the Specimen Collected for Bleeding Time Blood Test?
Following is the specimen collection process for Bleeding Time Blood Test:
Sample required: Blood
Process of obtaining the blood sample:
- Inflating a blood pressure cuff on the upper arm
- Making two small incisions in the lower arm
- And, measuring cessation of bleeding every 30 seconds
Preparation required: No special preparation is needed prior to the test.
What is the Significance of the Bleeding Time Blood Test Result?
A high value for the Bleeding Time Blood Test may indicate:
- von Willebrand disease
- Blood clot formation inside blood vessels (thrombosis)
The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.
Additional and Relevant Useful Information:
- The Bleeding Time Blood Test is not often performed in modern clinical practice. Currently, more sophisticated and standardized methods are used
Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider of the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.