Analytical performance of the VITA™ point-of-care CD4 enumeration assay

CD4+ T-cell enumeration remains critical for management of people with HIV (PWH). In resource-limited settings, point-of-care CD4 testing can increase accessibility and decrease turnaround time compared to flow cytometry. This study evaluated the performance of VITA point-of-care CD4 (Accesso Biotech; VITA CD4) compared to AQUIOS (Beckman Coulter; AQUIOS) flow cytometry. Remnant venous blood samples from PWH with known CD4 counts on FDA-cleared AQUIOS flow cytometry were tested twice with VITA CD4. Statistical analyses included descriptive statistics, correlation analysis, Bland-Altman agreement analysis, and Passing-Bablok regression. The coefficient of variation was calculated on duplicate measurements. The University of San Francisco Institutional Review Board approved the study. VITATM CD4 results showed strong correlation with AQUIOS flow cytometry (r = 0.973, p < 0.001). Bland-Altman analysis revealed a mean bias of -48.9 cells/{micro}l (95% CI: -61.8 to -36.0), with limits of agreement from -231.1 to 133.3 cells/{micro}l. For samples <500 CD4 cells/{micro}L (n=137), the mean bias was reduced to -8.6 cells/{micro}l (95% CI: -17.8 to 0.6). Passing-Bablok regression suggested a small constant positive bias and proportional bias at counts above 500 cells/{micro}l [y = 30.2 (95% CI: 19.3 to 44.2) + 0.83x (95% CI: 0.80-0.86)]. The coefficient of variation for duplicate VITA POC CD4 measurements was 11.86%. VITA CD4 results correlated strongly with flow cytometry at clinically relevant CD4 values. Its diagnostic performance and applicability at point-of-care make it a promising CD4 tool, also in settings with limited laboratory infrastructure. Further clinical validation and assessment of user acceptability is recommended.