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This sample had a reasonably normal WBC count and differential, but the results were accompanied by an NWBC (non-white blood cell) flag. The Size versus Complexity plot was abnormal and showed a clear population of events adjacent to the lymphocyte population and below the size threshold. These events triggered the NWBC flag.


The NWBC flag can be triggered by a number of different factors including low numbers of nucleated red blood cells (NRBC), lyse-resistant RBC (RRBC), platelet clumps, or giant platelets. Examination of scatterplots, together with consideration of the other hematological parameters, can often provide clues as to the reason for an NWBC flag. In this example, the white blood cell count and the red cell parameters were normal, but there was an apparent moderate thrombocytopenia of 79.7 x 10^9/L. In addition, the 0º/ RBC 10º scatterplot demonstrated a cluster of black events, just above the platelet cluster. All of these are suggestive of platelet clumps and this was confirmed by reference microscopy. The low platelet count was consequently interpreted as pseudo-thrombocytopenia.

Numerical Results

WBC 6.45 10e3/μL
NEU 2.811 43.56 %
BLST 0.00 0.00 % NBWC
MONe .603 9.35 %
EOS .169 2.61 %
BASO .075 1.16 %
LYM 2.794 43.32 %

RBC 4.15 10e6/μL
HGB 12.6 g/dL
HCT 36.1 %
MCV 86.9 fL
MCH 30.3 pg
MCHC 34.8 g/dL
RDW 10.7 %

PLT 79.7 10e3/μL
MPV 7.69 fL

CELL-DYN Ruby Casebook. NWBC Flag. 2018. ADD-00005070. p.48
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