COULTER HmX Hematology Analyzer, Reference Manual

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PN 4237523A 3-12
OPERATION PRINCIPLES
COUNTING AND SIZING
Plt Fitting Process
Having checked that the Plt count per period is greater than 20 x 10
3
cells/µL, the computer
smooths the histogram from each count, and finds a maximum point and two minimum
points in each histogram. It uses a least-squares method for a log-normal curve to fit a portion
of the histogram between the two minimum points. It then checks that each of the fitted
curves is positive, has a mode between 3 and 15 fL, and has a PDW greater than
approximately 20%. It votes on Plt, MPV, and PDW derived from the fitted curves. These
fitted curves have a range of 0 to 70 fL. If any of the criteria above are not met, an R flag
appears next to Plt and MPV.
For no-fit conditions, the computer derives the Plt count from the portion of the histograms
between the two minimum points, then votes on Plt, MPV, and PDW derived from the raw
data
.
Scatterplot Development
The system performs a series of operations on the stored digital raw data values to identify
subpopulations and calculate percentage values. It also produces the scatterplot displays for
visual representation of the WBC and Reticulocyte/RBC populations. A scatterplot is a
two-dimensional graphic display of the results of the volume, conductivity, and scatter
measurements. Largest concentration is indicated on the scatterplot display by intensity.
Differential-Related
The discriminant function (DF) 1 scatterplot, Figure , shows lymphocyte
e
, monocyte
B
,
neutrophil
C
, and eosinophil
D
populations. The basophil population is behind the upper
right quadrant of the lymphocyte
e
population. For purposes of the display, the axes are
labeled: Volume and DF 1. DF 1 is derived primarily from the light scatter measurement.
Volume is determined by the low-frequency impedance measurement.
Figure 3.12 Scatterplot, DF 1 View