ABSTRACT
Use of the standard dual-platform flow cytometric method for determination of CD4+ T-lymphocyte counts, which needs both a flow 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, CyFlowgreen (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 (R
2 = 0.96; mean bias, −69.1 cells/μl; 95% confidence interval [CI], −225.7 to +87.5 cells/μl) and the FACSCount system (R
2 = 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 (R
2 = 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 CyFlowgreen 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.
Relationship between Infectious Cell-Associated Human Immunodeficiency Virus Type 1 Load, T Lymphocyte Subsets, and Stage of Infection in Homosexual Men