Evaluation of a cost-effective gating strategy for CD4+T lymphocyte enumeration in HIV-infected individuals via flow cytometry

Background: Monitoring CD4+ T lymphocyte levels is a cornerstone in managing HIV infection, essential for assessing immune status and determining treatment strategies. However, the high cost of standard flow cytometry methods limits access to these diagnostic tools in low-income settings. This study evaluates a costeffective alternative method (AM) with a simplified gating strategy and reduced antibody use compared to the standard method (SM), which is based on PanLeucogating (PLG). Methods: This multicenter study analyzed 1,001 HIV-positive patient samples in a central laboratory serving six hospitals in Istanbul. SM used four antibodies (CD45/CD3/CD4/CD8), while AM utilized only CD4/CD8. Flow cytometric analysis was performed on a BD FACS Canto II system, and CD4* T cell percentages were compared between methods using Pearson's correlation coefficient and the Mann-Whitney U test. Results: A strong correlation (r = 0.993, p < 0.001) was observed between AM and SM, with no statistically significant difference (p = 0.339). However, AM systematically reported lower CD4* percentages, likely due to the absence of CD3-based gating and the use of FS/SS plots instead of CD45 for gating lymphocytes. Conclusion: With one of the largest datasets among similar studies, our findings suggest that AM, which uses 50 % fewer antibodies, is a cost-effective and viable alternative for CD4* enumeration in HIV monitoring. However, further validation in diverse epidemiological settings and clinical impact assessments are required before widespread clinical implementation.