Assuming normal platelet function, decreases in platelet count below normal may be associated with a proportionate increase in bleeding time.

If the platelet count is over 100,000 per microliter, the normal bleeding time is 3-8 minutes.


If the platelet count is under 10,000 per microliter, then the bleeding time cannot be predicted from the platelet count.


For platelet counts between 10,000 and 100,000 platelets/uL, the bleeding time bears a relationship to the platelet count as follows:


predicted bleeding time assuming normal platelet function =

= (30.5 - ((platelet count) / 3850))


If the platelet count is between 10,000 and 100,000 and if the actual bleeding time is more than the predicted time by "a certain limit," then a qualitative platelet defect is likely present. If the actual bleeding time is less than the predicted bleeding time, then some people hypothesize a higher percentage of "young" platelets, which are functionally more active than "older" platelets.

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