Bleeding Time (BT)

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Subject: Bleeding Time (BT)

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Definition

  • BT is a functional test for primary hemostasis (platelets and small vessels), infrequently performed nowadays (see below under limitations).

  • Normal range: 4–7 minutes (slightly longer in women).

Use

  • The method of Ivy as modified by Mielke, using a commercially available template, is the best standardized way to perform BT. A blood pressure cuff on the upper arm is inflated to 40 mm Hg, two small skin incisions are made through the template on the volar surface of the forearm, and cessation of bleeding is counted every 30 seconds.

  • BT may be used when better standardized equipment is not available for:

    • Workup of patients with the suspected diagnosis of a platelet defect or von Willebrand disease. Note the extreme variability of BT in patients with von Willebrand disease.

    • Monitoring hemostatic therapy for patients diagnosed with bleeding associated with von Willebrand disease, a thrombocytopathy, or uremia (creatinine >1.1 mg/L impairs hemostasis).

    • Prior to kidney biopsy in patients with uremia.

Interpretation

  • BT is not proven to be of value in the following conditions:

    • Patients with liver disease

    • Patients prior to general surgery, coronary bypass, or coronary stent insertion

    • Patients prior to orthopedic, ear–nose–throat, or neurosurgery

    • In the follow-up of patients receiving ASA, NSAIDs, or antiplatelet drugs (clopidogrel, prasugrel)

    • Patients with myeloproliferative neoplasms or myelodysplastic syndromes

  • BT is contraindicated when platelet counts are <50,000 cells/μL because it may be difficult to arrest bleeding at the incision site and the test may be noncontributory.

  • BT is not prolonged in coagulation disorders such as the hemophilias.

Limitations

  • These include the operator's variability in technique, limited precision, accuracy, reproducibility, and also variability in the same patients at different times. “In vitro” BT equipment, such as platelet function analyzer (PFA 100), is better standardized and has better reproducibility.

  • Many health care organizations have discontinued the use of BT entirely.

 
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