MANUAL CELL COUNTS
Section I. MANUAL COUNTS, BLOOD SPECIMENS
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
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.
WHITE BLOOD CELL COUNT
a. Principle. A sample of whole blood is mixed with a weak acid solution that
lyses nonnucleated red blood cells. Following adequate mixing, the specimen is
introduced into a counting chamber where the white blood cells (leukocytes) in a diluted
volume are counted.
b. Reagent. White-count diluting fluid. Either of the following diluting fluids may
(1) Two percent acetic acid . Add 2 ml glacial acetic acid to a 100 ml volumetric
flask. Dilute to the mark with distilled water.
(2) One percent hydrochloric acid. Add 1 ml hydrochloric acid to a 100 ml
volumetric flask. Dilute to the mark with distilled water.