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ISSN 1027-2852 (Electronic)
ISSN 0864-4551 (Print)

2019, Number 1

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Biotecnol Apl 2019; 36 (1)

Strong impact of the side scatter channel performance in the volumetric flow cytometer CD4+ T cell counts using the CD4% easy count kit

Iglesias E, Hernández-Requejo D, Godínez-López MC, Vazquez-Arteaga A

Language: English
References: 24
Page: 1301-1306
PDF size: 827.53 Kb.


ABSTRACT

The absolute number and percentage of CD4+ T cells are important parameters in the follow up of HIV-1-infected patients. However, discordant results were found between the CD4+ cell counts and percentage of cells, determined by flow cytometry using the CD4% easy count kit from Sysmex-Partec®. This is a validated kit based on a single-platform methodology for volumetric cytometry counting, and deviations were present despite quality controls were in the acceptable range. Therefore, the photomultiplier performance was analyzed as the possible source of deviation, using pre-counted beads, for the individual channels: side scatter (SSC), fluorescence 1 (FL-1) and FL-2 used in the CD4% easy count kit. Additionally, forward scatter (FSC) and FL-3 were selected for comparison. Then, the coefficients of variation (CV) and accuracy were calculated and beads concentration (count/mL) obtained within the peak of histograms in every optical channel and compared by linear regression analysis. CV, accuracy and linear regression analysis showed fine goodness-of-fit for all channels, but the slope of the SSC was shown statistically different (p < 0.01), suggesting bad performance on that channel. Other minor deviations were recorded comparing the intercept of the FSC to FL-1 (p = 0.03) and FL-3 (p = 0.02). Our results explained previous discordances using the CD4% easy count kit and revealed a previously unappreciated limitation of routine quality controls. They provide new routine quality controls which can be incorporated to detect photomultiplier’s error in any flow cytometer even without significant deterioration of performance.


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