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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 .
The blood may also be irradiated, which destroys the DNA in the white cells and prevents graft versus host disease, which may happen if the blood donor and recipient are closely related, and is also important for immunocompromised patients. Other modifications, such as washing the RBCs to remove any remaining plasma, are much less common.
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]
A complete blood count (CBC), also known as a full blood count (FBC), is a set of medical laboratory tests that provide information about the cells in a person's blood.The CBC indicates the counts of white blood cells, red blood cells and platelets, the concentration of hemoglobin, and the hematocrit (the volume percentage of red blood cells).
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.
Higher platelet transfusion thresholds have been used in premature neonates, but this has been based on limited evidence. [19] There is now evidence that using a high platelet count threshold (50 x 10 9 /L) increases the risk of death or bleeding compared to a lower platelet count threshold (25 x 10 9 /L) in premature neonates. [20]
They circulate in the blood of mammals and are involved in hemostasis, leading to the formation of blood clots. Platelets release thread-like fibers to form these clots. The normal range (99% of population analyzed) for platelets is 150,000 to 450,000 per cubic millimeter. [6] If the number of platelets is too low, excessive bleeding can occur.
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]