COULTER HmX Hematology Analyzer, Reference Manual

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PN 4237523A 3-10
OPERATION PRINCIPLES
COUNTING AND SIZING
3.5 COUNTING AND SIZING
Red and White Blood Cell Counting
Routine Counting
Each bath has one aperture. The regulated vacuum draws a precise volume of sample dilution
through each aperture. At each aperture, the system counts cells in three consecutive periods
of 4 seconds each. During each counting period, the analyzer gathers and amplifies the cell
pulses. It also checks that WBC and RBC data accumulations are above a predetermined low
cut-off value.
Pulses from the RBC bath that represent cells as 36 fL or greater are classified as red cells.
Pulses from the WBC bath that represent cells as 35 fL or greater are classified as white cells.
Both counts then go to the computer for coincidence correction and voting.
Extended Counting
If accumulations are too low, the unit extends the sensing period. This ensures that the
size-distribution curves accurately reflect the true cell population.
Coincidence Correction
Occasionally, more than one cell goes through the aperture at the same time. When cells
coincide, however, the analyzer counts only one pulse. Because the frequency of coincidence
is proportional to the actual count, the system easily corrects results for coincidence.
Triplicate Counting/Voting
The HmX Hematology Analyzer and HmX Hematology Analyzer with Autoloader use
triplicate counting, strict voting criteria, and proprietary flagging algorithms to confirm
parameter results prior to reporting. After coincidence correction, the system compares the
data from the three count periods then votes and rejects any questionable data. Voting occurs
for: WBC, RBC, Plt, MCV, RDW, and MPV. If the system finds disagreement among all the
count periods or some other internal criteria are not met, the system displays and prints a
total voteout code (– – – – –) instead of the parameter result.
Beckman Coulter uses triplicate counting and voting to maximize the accuracy of the results.
IMPORTANT In rare instances, especially for specimens where fibrin, cell fragments, or other debris are
likely to occur, such as pediatric and oncology specimens, a transient or partial aperture blockage may not
be detected by any of these methods. Therefore, verify flagged results for accuracy and review any result
which exceeds your laboratory action limits.