4-10 Running a Sample
4.7.1 Histograms
In five-part differential mode, histograms display population distributions of each cell type: leukocytes
(white blood cells — WBC), eosinophils (EOS), erythrocytes (red blood cells — RBC), and thrombo-
cytes (platelets — PLT). The histograms show the relative frequency of cells on the vertical (Y) axis,
and cell volume in femtoliters (fl) on the horizontal (X) axis.
Histograms enable you to quickly scan results for abnormalities, and also allow the versed practitioner
to derive more information about the sample than is displayed by the values alone. The following pages
describe each of the histograms (WBC, EOS, RBC, and PLT), and show a typical example of each with
an explanation.
4.7.1.1 White Blood Cell Histogram (WBC)
WBC histograms show white blood cell populations
sorted by size. Cells larger than discriminator 1 are
counted as WBCs. Blood includes three WBC popula-
tions:
Lymphocytes (LYM), shown by the first
peak in the histogram.
Monocytes (MON), indicated by the area
between the second and third discriminators
(although the MON region does demon-
strate a distinctive peak of its own, this peak is not always clear in histogram form).
Granulocytes (GRA) are the neutrophils, eosinophils, and basophils, indicated by the
peak to the right of the third discriminator.
4.7.1.2 Eosinophil Histogram (EOS)
The distribution of eosinophils is shown by the second
peak in the histogram. The first peak (dotted line) is the
RBC “ghost” and other WBCs.
4.7.1.3 Red Blood Cell Histogram (RBC)
The distribution of red blood cells normally appears as a
single, steep, bell-shaped curve. The presence of reticulo-
cytes and nucleated red blood cells (nRBCs) cause this
curve to widen.
LYM
discriminator 1
discriminator 2
discriminator 3
GRA
MON
33 95 102 400
WBC
(fl)
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