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In a typical set of rules, a platelet donor must weigh at least 50 kg (110 lb) and have a platelet count of at least 150 x 10 9 /L (150,000 platelets per mm³). [2] One unit has greater than 3×10 11 platelets. Therefore, it takes 2 liters of blood having a platelet count of 150,000/mm³ to produce one unit of platelets.
Thrombotic thrombocytopenic purpura (TTP) is a blood disorder that results in blood clots forming in small blood vessels throughout the body. [2] This results in a low platelet count, low red blood cells due to their breakdown, and often kidney, heart, and brain dysfunction. [1]
One common definition of thrombocytopenia requiring emergency treatment is a platelet count below 50,000/μL. [5] Thrombocytopenia can be contrasted with the conditions associated with an abnormally high level of platelets in the blood – thrombocythemia (when the cause is unknown), and thrombocytosis (when the cause is known). [6] [7]
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 concentration in the blood (i.e. platelet count), can be measured manually using a hemocytometer, or by placing blood in an automated platelet analyzer using particle counting, such as a Coulter counter or optical methods. [47] Most common blood testing methods include platelet count in their measurements, usually reported as PLT. [48]
Tests in platelet rich plasma (close to real conditions in the body, but restrictions as to the terms of work), Tests in whole blood (the most adjusted to human physiology; the test can be started immediately; but the least convenient due to terms of blood storage and difficulties of the results' interpretation).
Diagnosis of ITP involves identifying a low platelet count through a complete blood count, a common blood test. However, since the diagnosis relies on excluding other potential causes of a low platelet count, additional investigations, such as a bone marrow biopsy , may be necessary in certain cases.
High platelet counts can occur in patients with polycythemia vera (high red blood cell counts), and is an additional risk factor for complications. [ citation needed ] A very small number of people report symptoms of erythromelalgia , a burning sensation and redness of the extremities that resolves with cooling, or aspirin or both.