Comparison of 5 flow cytometric immunophenotyping systems for absolute CD4⁺ T-lymphocyte counts in HIV-1-infected patients living in resource-limited settings

Enumeration of CD4⁺ T lymphocytes is important in management of HIV-infected patients. However, CD4 testing by current gold standard bead-based flow cytometer (FCM) system is expensive for developing countries. This study compared 2 affordable volumetric FCMs with the 3 predicate FCM systems. CD4 ⁺ T-lymphocyte counts on blood samples from 150 HIV-1-infected Thai patients were determined in parallel by 5 FCM systems: the 2 single-platform volumetric FCM systems, Guava and CyFlow^green; the 2 standard single-platform bead-based systems (2-color FACSCount and the TriTEST/TruCOUNT tube using a FACSCalibur FCM); and the dual-platform TriTEST system. Correlation and agreement were analyzed using linear regression and Bland-Altman analysis. Results from these 2 volumetric systems gave similar results and excellent correlation: R² > 0.93; mean biases ranged from +6.3 to +24.1 cells per microliter more for the Guava. In contrast, the CyFlow^green showed the lowest values with R² > 0.97; mean biases ranged from -9.8 to -27.6 cells per microliter. This indicates that the absolute CD4 ⁺ T-lymphocyte counts determined by CyFlow^green are <FACSCount<DP TriTEST< TriTEST/TruCOUNT<Guava. Although the use of these 2 volumetric FCMs could make CD4⁺ T-lymphocyte enumeration more affordable in resource-poor settings, variations among these systems should be considered if these are to be interchanged.