Bleeding Time

        The bleeding time test is approximately 170 years old and was developed even before platelets were recognized as normal blood elements. The test was used to evaluate patients who presented with purpura. Current thinking is that the test evaluates platelet function, provided that the platelet numbers are adequate. There are a few reports of prolongation in coagulation factor deficiencies and with patients on heparin.
      The test has very poor sensitivity. For example, the test will detect only 27% of patients with von Willebrand’s syndrome (whereas symptoms alone have a sensitivity to von Willebrand’s of 65%). To investigate bleeding, take a good history and use this test as part of a battery of tests.
     Our reference range is 1-9 minutes but given a positive history of bleeding, be suspicious in the borderline area ( 7 min.). The test lacks sensitivity therefore, you should fully investigate all abnormal findings. It is very difficult to define false positives as many bleeding tendencies are never fully explained with today’s models.

Evaluations of the bleeding time indicate that you should not use the test:

for preoperative screening.

to rule out a bleeding disorder (for example: to prove child abuse).

to clear a patient for surgery given clinical evidence of bleeding, other laboratory abnormality(ies) or a positive history of bleeding.

The test is simply too insensitive and misses over three-fourths of bleeding disorders due to platelet dysfunction.

The bottom line? As originally intended, use this test to investigate purpura. Do not use the test to predict bleeding nor to justify other procedures. Normal results are practically meaningless. A good history has been shown, repeatedly, to be more sensitive to bleeding disorders than any hemostatic screening test.