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Low levels of platelets in turn may lead to prolonged or excessive bleeding. It is the most common coagulation disorder among intensive care patients and is seen in a fifth of medical patients and a third of surgical patients. [3] A normal human platelet count ranges from 150,000 to 450,000 platelets/microliter (μL) of blood. [4]
This results in platelet activation and the formation of platelet microparticles, which initiate the formation of blood clots; the platelet count falls as a result, leading to thrombocytopenia. [1] [7] In addition, the reticuloendothelial system (mostly the spleen) removes the antibody-coated platelets, further contributing to the thrombocytopenia.
Thrombotic thrombocytopenic purpura (TTP) initially presents with a range of symptoms that may include severe thrombocytopenia (platelet count usually < 30,000/mm³), microangiopathic hemolytic anemia (evidenced by schistocytes in the blood smear), and various clinical signs such as petechiae, purpura, neurologic symptoms, myocardial ischemia ...
Platelets derived from the abnormal megakaryocytes are activated, which, along with the elevated platelet count, contributes to the likelihood of forming blood clots. [8] The increased possibility of bleeding when the platelet count is over 1 million is due to von Willebrand factor (vWF) sequestration by the increased mass of platelets, leaving ...
Normal count is in the range of 150 × 10 9 to 450 × 10 9 platelets per liter of blood, [1] but investigation is typically only considered if the upper limit exceeds 750 × 10 9 /L. When the cause is unknown, the term thrombocythemia is used, as either primary thrombocythemia or essential thrombocythemia .
Platelet satellitism. Platelet rosetting, or satelliting, around white blood cells can lead to undercounting by automated analyzers. [5] Clotted samples. Coagulation within the sample leads to undercounting, because the analyzer samples the liquid part of the blood, while some of the platelets remain in the tube, trapped in the clot.
Platelet transfusion alone is normally not recommended except in an emergency and is usually unsuccessful in producing a long-term platelet count increase. This is because the underlying autoimmune mechanism that is destroying the patient's platelets will also destroy donor platelets, and so platelet transfusions are not considered a long-term ...
Bleeding time may be affected by platelet function, certain vascular disorders and von Willebrand Disease—not by other coagulation factors such as haemophilia.Diseases that may cause prolonged bleeding time include thrombocytopenia, disseminated intravascular coagulation (DIC), Bernard-Soulier disease, and Glanzmann's thrombasthenia.