Beckman Coulter COULTER LH 750 System, Reference

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PN 4277248DD
3-10
OPERATION PRINCIPLES
COUNTING AND SIZING
Coincidence Correction
Occasionally, more than one cell passes through the aperture at the same time. When cells
coincide, the Analyzer counts only one pulse. As the frequency of coincidence is proportional
to the actual count, the system automatically corrects results for coincidence.
Voting
To prevent data errors due to statistical outliers or obstructions that may block an aperture,
the Analyzer votes on the data from all of the apertures, and rejects any questionable data. For
the WBC count, RBC count, MCV, RDW, Plt count, and MPV, the Analyzer computer
compares the data from the three apertures. It verifies that at least two apertures have
produced data within an established statistical range of each other.
If the data from one aperture is outside the established statistical range, the computer votes
out the data and histograms from that aperture. The computer derives the affected parameter
by averaging the data from the two remaining apertures.
The data from at least two of the three apertures must be within an established statistical
range of each other, or the system totally votes out the parameter and histograms. When a
parameter totally votes out, the system does not give any results for the affected parameter or
for any parameters that are derived from it. See Flags and Codes for messages that appear in
these circumstances.
Pulse Editing
When cells pass through the aperture near the edge or at an angle rather than at the center,
they create atypical pulses. The RED/WHITE PROCESSOR card edits RBC and WBC pulses to
exclude these atypical pulses from analysis because they distort the true size of the cell. This
prevents the atypical pulses from influencing size measurement. Each of the six apertures has
an editor.
Sweep Flow
The sweep flow is a steady stream of diluent that flows behind the RBC aperture during the
sensing period. This prevents cells from re-entering the sensing zone and being counted as
platelets. See Figure 3.5.