Ann Lab Med.  2015 Jan;35(1):28-34. 10.3343/alm.2015.35.1.28.

Flow Cytometric White Blood Cell Differential Using CytoDiff is Excellent for Counting Blasts

• Kahng J
• Kim Y
• Kim M
• Oh EJ
• Park YJ
• Han K

• KMID: 2363144
• DOI: http://doi.org/10.3343/alm.2015.35.1.28

Abstract

BACKGROUND
The usefulness of the CytoDiff flow cytometric system (Beckman Coulter, USA) has been studied in various conditions, but its performance including rapidity in detecting and counting blasts, the most significant abnormal cells in the peripheral blood, has not been well evaluated. The objective of this study was to evaluate the performance of the CytoDiff differential counting method in challenging samples with blasts.
METHODS
In total, 815 blood samples were analyzed. Samples flagged as "blasts" or "variant lymphocytes" and showing <10% blasts by manual counts were included. In total, 322 samples showed blasts on manual counts, ranging from 0.5% to 99%. The CytoDiff method was performed by flow cytometry (FC500; Beckman Coulter, USA) with a pre-mixed CytoDiff reagent and analyzing software (CytoDiff CXP 2.0; Beckman Coulter).
RESULTS
The average time required to analyze 20 samples was approximately 60 min for manual counts, and the hands-on time for the CytoDiff method was 15 min. The correlation between the CytoDiff and manual counts was good (r>0.8) for neutrophils and lymphocytes but poor (r<0.8) for other cells. When the cutoff value of the CytoDiff blast count was set at 1%, the sensitivity was 94.4% (95% CI; 91.2-96.6) and specificity was 91.9% (95% CI; 89.0-94.1). The positive predictive value was 88.4% (95% CI; 84.4-91.5) (304/344 cases) and negative predictive value was 96.2% (95% CI; 93.9-97.7) (453/471 cases). The CytoDiff blast counts correlated well to the manual counts (r=0.9223).
CONCLUSIONS
The CytoDiff method is a specific, sensitive, and rapid method for counting blasts. A cutoff value of 1% of at least 1 type of blast is recommended for positive CytoDiff blast counts.

Keyword

CytoDiff; Flow cytometry; Differential; Blasts; Performance

MeSH Terms

Adult
Female
Flow Cytometry/*instrumentation
Humans
Leukocyte Count
Leukocytes/*cytology
Lymphocytes/cytology
Male
Neutrophils/cytology

Figure

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  Fig. 1 An example of CytoDiff results. Seventeen cell populations are displayed in different colors with complicated gates.

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  Fig. 2 Binomial envelopes and correlations of CytoDiff counts of neutrophils, lymphocytes, monocytes, eosinophils, immature granulocytes, and blasts to the manual counts. The blasts showed good correlation to each other (r2=0.9246).

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  Fig. 3 Cases showing a positive manual blast count but <1% CytoDiff blast count. The manual blast count was 0.5% in (A) and (B) but 12% in (C). There were characteristic blast populations (red dots) on the CD45/SS plots in (A) and (B). (C) shows a typical leukemic monocyte population by promonocytes (light green dots). Some of the cases showing a positive manual blast count but <1% CytoDiff blast count did not show characteristic blast populations on CD45/SS plot.

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  Fig. 4 Cases showing no manual blasts on the first count but 0.5% on the second count and showing >1% CytoDiff blast counts. All of the cases show characteristic low SS/low CD45 blast populations (red dots, arrows) on the CD45/SS plots.

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  Fig. 5 A case showing 16% manual IG count and 54.98% CytoDiff IG count. The smear shows (A) 2 lymphocytes and a neutrophil in the ideal zone (Wright-Giemsa stain,×200), (B) many large cells aggregated at the end of the smear (Wright-Giemsa stain,×200), and (C) mainly IGs larger than eosinophils (arrow) (Wright-Giemsa stain,×1,000).

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