Bleeding time is a laboratory test to assess platelet function and the body’s ability to form a clot. The test involves making a puncture wound in a superficial area of the skin and monitoring the time needed for bleeding to stop (ie, bleeding site turns "glassy").
Bleeding normally stops within 1-9 minutes but may be longer in children (1-13 minutes) and tends to take slightly longer in females than in males.
Special Note: The Bleeding Time is a historical footnote in the archives of laboratory medicine. At the current time, it has been largely discredited and, in part, replaced by other testing. It is included in this collection of other laboratory tests for the convenience of our readers, who may see a reference to the Bleeding Time from older medical literature.
General interpretations of bleeding time are as follows:
1-9 minutes: Normal
9-15 minutes: Platelet dysfunction
More than 15 minutes: Critical; test must be discontinued and pressure should be applied
A bleeding time evaluation is used to measure the primary phase of hemostasis, which involves platelet adherence to injured capillaries and then platelet activation and aggregation. The bleeding time can be abnormal when the platelet count is low or the platelets are dysfunctional. Causes of abnormal bleeding time can be hereditary or acquired.
Hereditary causes of abnormal bleeding time are as follows:
Acquired causes of abnormal bleeding time are as follows:
Medications (aspirin, nonsteroidal anti-inflammatory drugs [NSAIDs], antibiotics [penicillin, cephalosporins], anticoagulants [eg, heparin, streptokinase], tricyclic antidepressants, antipsychotics, theophylline)
Vitamin C deficiency
Collection and Panels
The patient should not take aspirin, NSAIDs, or alcohol for 7 days prior to the test, since they will prolong the bleeding time and lead to false-positive results.
This is the most commonly used method.
A blood pressure cuff is applied to the arm and inflated to 40 mm Hg. The patient’s forearm is then cleaned with alcohol, and an incision is made with a sterile blade or scalpel, 1 mm deep and 10 mm long. Since the test is directed to capillary vessels, the area should have no large vessels.
Immediately, a stopwatch starts recording time. Then, every 30 seconds, a filter paper is applied gently over the wound. Whenever the paper absorbs blood, it means that the bleeding is active and has not stopped. This is repeated every 30 seconds until the bleeding stops completely (ie, no more blood is being absorbed by the filter). After the bleeding stops, the blood pressure cuff should be deflated. The bleeding time is defined as the time from the incision until all bleeding has stopped.
This technique is similar to the Ivy method; however, no blood pressure cuff is needed. In addition, it is less invasive, since it involves making a puncture wound that is 3 mm deep after the area is cleaned with alcohol. Areas with no large vessels are preferred, such as earlobe. Then, with a filter paper, the wound is swabbed every 30 seconds until no more blood is absorbed.
Although the Ivy method is more invasive, it is preferable, since its results are more reproducible.
The Bleeding Time is a historical footnote in the archives of laboratory medicine. At the current time, it has been largely discredited and, in part, replaced by other testing. It is included in this collection of other laboratory tests for the convenience of our readers, who may see a reference to the Bleeding Time from older medical literature.
Hemostasis is a sequence of events that leads to bleeding cessation via the formation of a fibrin-platelet hemostatic plug. It involves the triad of an injured vascular wall, platelets, and coagulation cascade. Once platelets are exposed to endothelial cells and collagen in the injured vascular wall, von Willebrand factor (vWF) is released, and platelets become activated and adhere to collagen through vWF. Injured cells release tissue factor, which activates factor VII (extrinsic pathway), and the exposure of thrombogenic subendothelial collagen activates factor XII (intrinsic pathway).
Platelets play a major role in hemostasis, starting with adherence to the injured wall through vWF, which adheres to subendothelial collagen. Platelets then adhere to vWF via glycoprotein Ib. After adherence occurs, platelet activation takes place, whereby they change in shape with degranulation and thromboxane A2 synthesis. Soon thereafter, platelet aggregation occurs, whereby additional platelets are recruited from the bloodstream and aggregate via adenosine diphosphate (ADP) and thromboxane A2 and bind to each other by binding to fibrinogen using GP IIb-IIIa, thus forming a fibrin-platelet plug.
The bleeding time reflects this process, and, if the platelets do not function properly in any of these steps, the bleeding time will prolong.
Since platelets are the major factor in primary hemostasis, the bleeding time is the main indicator of this function; thus, measuring bleeding time in patients with bleeding disorders is a reasonable approach.
It is very useful as a screening test in the outpatient setting before invasive procedures, especially in patients with known hemorrhagic disorders, in order to predict the probability of perioperative bleeding.
A bleeding time evaluation is most helpful in a patient with clinical bleeding whose platelet count and results of coagulation studies (PT/INR, aPTT) are normal. In this setting, the bleeding time will help recognize dysfunctional platelets.