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The bleeding time in pediatrics
1Universitäts-Kinderklinik, Freiburg, Germany.
Insights
The bleeding time (BT) test assesses primary hemostasis and is valuable for diagnosing bleeding disorders, especially in pediatrics. When prolonged, it indicates potential defects in platelets or clotting factors, guiding therapy and surgical risk assessment.
Area of Science:
- Hematology
- Clinical Pathology
- Pediatric Medicine
Background:
- The bleeding time (BT) test evaluates primary hemostasis, influenced by platelets, blood cells, vascular factors, hormones, and temperature.
- Variations within normal limits are physiologically expected and clinically insignificant.
Observation:
- Prolonged BT values, exceeding the upper normal limit, suggest potential defects in primary hemostasis.
- These defects may include thrombocytopenia, thrombocytopathy, anemia, leukopenia, or deficiencies in factors like von Willebrand factor (vWF).
Findings:
- The BT serves as a valuable screening test for patients presenting with bleeding symptoms.
- It is particularly informative in pediatrics, where primary hemostasis defects are more prevalent than coagulopathies.
- The BT can guide therapeutic interventions by reflecting clinical improvement.
Implications:
- When used preoperatively, BT should be complemented by activated partial thromboplastin time (aPTT) to detect coagulopathies.
- Standardized BT offers a reliable method for diagnosing hemostatic disorders, guiding treatment, and anticipating surgical bleeding risks.
- Its suitability for pediatrics stems from minimal blood requirement, avoidance of venipuncture, immediate results, and in vivo assessment of primary hemostasis.
Abstract:
When performed with standardized methods and techniques, the bleeding time (BT) depends on variables that physiologically alter primary hemostasis. These variables include number of platelets and platelet function, white and red blood cell counts, vascular factors, hormones, and temperature. Variations within normal limits reflect the in vivo situation and are of no clinical relevance. If the BT is prolonged far above the upper normal limit, however, defects of primary hemostasis have to be anticipated. These include thrombocytopenia or thrombocytopathy, anemia, leukopenia, and deficiencies of plasmatic factors such as von Willebrand factor (vWF), fibrinogen, the lupus anticoagulant, and factor V. The BT can be used as screening test for patients with bleeding symptoms. As a single test, the BT gives the best information in pediatrics, in which defects of primary hemostasis are more common than coagulopathies. In addition, BT can guide the therapy of these patients, because it reflects clinical improvement. When used as a preoperative screening test, BT should be combined with the activated partial thromboplastin time (aPTT) because BT usually does not recognize patients with coagulopathies. With standardized techniques and the knowledge of its merits and limitations, BT is a useful test for diagnosing hemostatic disorders, guiding their therapy, and warning of unexpected bleeding complications during surgery. The BT is especially suited for use in pediatrics for the following reasons: (1) It does not require a venipuncture and is similar to capillary blood sampling if performed with standardized devices adapted for pediatric use; (2) it is an in vivo test informing mostly on defects of primary hemostasis, which are the most common bleeding diatheses in childhood; (3) the results are immediately available; (4) it requires only minimal amounts of blood; and (5) it does not require unphysiological reagents and preparation of the sample. The test requires a highly motivated and experienced operator who knows of the many variables influencing the BT. The interpretation cannot be done without knowledge of the history and physical status of the patient and of the limitations of the BT.