a. Blood cells are subject to quantitative variations as well as the qualitative variations described in Lesson 4. Some diseases stimulate the production of blood cells while others prevent or diminish the production of blood cells. For this reason a cell count gives valuable information to the physician concerning his patient's condition. Furthermore, in the case of the leukocyte count, the total count is necessary to calculate absolute counts for each type of leukocyte. This is done by multiplying the total count by the percentage of the particular cell type.
b. Cell counts can be performed by a variety of methods. Erythrocytes and leukocytes are counted by manual methods or automated methods. Other cell counts are performed only by manual methods. It is important when performing a cell count to maintain good quality control. Great care should be taken when performing any cell count.
c. The following paragraphs outline procedures for white blood cell (WBC) count, total eosinophil count, and reticulocyte count. The WBC counts are routinely done; they are performed either by the hemacytometer method (manually) or by automated methods. Total eosinophil counts are performed by a hemacytometer method (manually) using special diluting fluids to accentuate these cells. Reticulocytes are demonstrated by using a supravital stain. Semen analysis and cerebrospinal fluid (CSF) counts use a hemacytometer to perform the procedure as well. They are included in the next section.