CELL-DYN
®
3200 System Operator’s Manual
3-11
9140181H—October 2001
Section 3
Principles of Operation
Figure 3.3 illustrates the measurement of light scattered during the WBC optical
measurement process.
The WBC count is determined by enumerating the number of occurrences above a
hardware threshold in the 0° channel. The information from all four measurements
is used to differentiate the WBCs into five subpopulations:
Neutrophils
Lymphocytes
Monocytes
Eosinophils
Basophils
The WBC data is presented graphically as a scatterplot. It may also be presented in
two histograms at operator request.
WBC Reagent
The
WBC reagent
used with the CELL-DYN 3200 instrument is the CELL-DYN
WBC Lyse. It is an integral part of the WBC analysis. White blood cells diluted in
the reagent maintain cellular integrity close to their native state. The structure of
the basophils changes slightly due to the hygroscopic nature of the basophilic
granules.
The RBCs are also altered by the reagent. The osmotic pressure of the RBC is
higher than that of the reagent. Therefore, the hemoglobin in the RBC diffuses out
of the cell and water from the reagent diffuses into the cell. The cell membrane
remains intact but the RBC now has the same refractive index as the sheath, thereby
rendering it invisible to the laser.
WBC Differential
The light scatter information is graphically presented in the form of scatterplots.
(The data can also be presented in histograms, available on request.) Each cell
analyzed is represented by a dot on the scatterplot. The dots are plotted at a point
determined by the intersection of the channel information designated on the X and
Y axes. For example, if a cell falls in channel 50 on the X axis and channel 50 on
the Y axis, it is plotted at the intersecting point of the two channels.
The scatter information may be plotted in various combinations to yield different
information. The CELL-DYN 3200 uses the scatterplots to differentiate the WBCs
into five subpopulations:
Neutrophils
Eosinophils
Lymphocytes
Basophils
Monocytes