t7.docx - Leukocyte Count Leukocytes unlike erythrocytes are completely colorless in their native state Another important physical difference is the

t7.docx - Leukocyte Count Leukocytes unlike erythrocytes...

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Leukocyte Count Leukocytes, unlike erythrocytes, are completely colorless in their native state. Another important physical difference is the stability of leukocytes in 3% acetic acid or saponins; these media hemolyze erythrocytes (though not their nucleated precursors). Türk’s solution, used in most counting methods, employs glacial acetic acid for hemolysis and crystal violet (gentian violet) to lightly stain the leukocytes. A 50-µl EDTA blood sample is mixed with 500 µl Türk’s solution in an Eppendorf tube and incubated at room temperature for 10 minutes. The suspension is again mixed and carefully transferred to the well of a prepared counting chamber using a pipette or capillary tube. The chamber is allowed to fill from a droplet placed at one edge of the well and placed in a moisture-saturated incubator for 10 minutes. With the condenser lowered (or using phase contrast microscopy), the leukocytes are then counted in a total of four of the large squares opposite to each other (1 mm2 each). The result is multiplied by 27.5 (dilution: 1 + 10, volume: 0.4 mm3) to yield the leukocyte count per microliter. Parallel (control) counts show variation of up to 15%. The normal (reference) ranges are given in Table 2. In an automated blood cell counter, the erythrocytes are lysed and cells with a volume that exceeds about 30 fl (threshold values vary for different instruments) are counted as leukocytes. Any remaining erythroblasts, hard-to-lyse erythrocytes such as target cells, giant thrombocytes, or agglutinated thrombocytes are counted along with the leukocytes, and this will lead to an overestimate of the leukocyte count. Modern analyzers can recognize such interference factors and apply interference algorithms to obtain a corrected leukocyte count. Visual leukocyte counts using a counting chamber show a variance of about 10%; they can be used as a control reference for automatic cell counts. Rough estimates can also be made by visual assessment of blood smears: a 40! objective will show an average of two to three cells per field of view if the leukocyte count is normal. Physiology and Pathophysiology of
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  • Spring '18
  • Mr. kanor
  • Hematology, Bone marrow, white blood cell, thrombocytes

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