Evaluation of a new single-parameter volumetric flow cytometer (CyFlow ^green) for enumeration of absolute CD4⁺ T lymphocytes in human immunodeficiency virus type 1-infected Thai patients

Abstract

Use of the standard dual-platform How cytometric method for determination of CD4+ T-lymphocyte counts, which needs both a How cytometer (FCM) and hematological analyzer, would inevitably lead to increased variability. The development of new single-platform (SP) FCMs that provide direct CD4+ T-lymphocyte counts for improved assay precision and accuracy have recently attracted attention. This study evaluated one of those systems, CyFlow green (Partec), a single-parameter SP volumetric FCM. The performance of CyFlowgreen was compared with those of two reference standard SP microbead-based technologies of the three-color TruCOUNT tube with the FACScan FCM and a two-color FACSCount system (Becton Dickinson Biosciences). Absolute CD4+ and CD8+ T-lymphocyte counts in 200 human immunodeficiency virus type 1-seropositive blood specimens were determined. Statistical analysis for correlation and agreement were performed. A high correlation of absolute CD4 counts was shown when those obtained with CyFlowgreen were compared with those obtained with the bead-based three-color TruCOUNT system (R2 = 0.96; mean bias, -69.1 cells/μl; 95% confidence interval [CI], -225.7 to +87.5 cells/μl) and the FACSCount system (R2 = 0.97; mean bias, -40.0 cells/μl; 95% CI, -165.1 to +85.1 cells/μl). The correlation of the CD4+ T-lymphocyte counts obtained by the two bead-based systems was high (R2 = 0.98). Interestingly, CyFlowgreen yielded CD4+ T-lymphocyte counts that were 21.8 and 7.2 cells/μl lower than those obtained with the TruCOUNT and the FACSCount systems, respectively, when CD4+ T-lymphocyte counts were <250 CD4+ T-lymphocyte counts/μl range or 17.3 and 5.8 cells/μl less, respectively, when CD4+ T-lymphocyte counts were <200 cells/μl. The single-parameter CyFlow green volumetric technology performed well in comparison with the performance of the standard SP bead-based FCM system. However, a multicenter comparative study is needed before this FCM machine is implemented in resource-limited settings. Copyright © 2005, American Society for Microbiology. All Rights Reserved.