Performance of the BD FACSPresto near to patient Analyzer in comparison with representative conventional CD4 instruments in Cameroon.
Authors: Sagnia Bertrand , Ghomsi Fabrice MBAKOP , Gutierrez Ana , SOSSO Samuel , KAMGAING Rachel , NANFACK Aubin Joseph , NJI Nadesh , AMBADA GEORGIA , LISSOM Abel , TCHOUANGUEU Thibaut Flaurant , Ndengkoh Loveline Ngu , DOMKAM Irenée , NCHINDA Godwin , NDJOLO Alexis 
Published: July 2020

Abstract
Background In view of scaling up viral load during the management of HIV in adults and children in resource limited settings, CD4+ T-lymphocyte count still relevant in remote areas where the decentralization of treatment is independent of viral load. Effective clinical management of HIV within these resource-constrained settings depends on affordable and reliable CD4+ T lymphocytes enumeration methods. We have assessed the performance of a BD FACSPresto POC which is a dedicated CD4 enumeration system applicable in remote areas. A comparative analysis was made between the performance of the BD FACSPresto POC and representative flow cytometry instruments present in Cameroon in including FACSCalibur, FACSCount, and PIMA POC from Becton Dickinson and ALERE respectively. All these CD4 enumerations are known to perform more than 5000 CD4 T cells tests per year. Methods: The BD FACSPresto POC CD4+ T cell technology was placed at CIRCB and operated by technician staff. 268 patients aged between 1 to 72 years old were included in the study. Participants were recruited from the Chantal BIYA international reference Center (CIRCB), Centre de Sante Catholique de NKOLODOM, Centre de Sante Catholique de BIKOP and CASS de Nkolndongo – Yaounde respectively. We compared the performance of the BD FACSPresto with three existing CD4 enumeration technologies including FACSCalibur, FACSCount and PIMA capable of performing more than 5000 tests per year. Bland – Altman method and correlation analysis were used to estimate mean bias and 95% limits of agreement and to compare the methods, including analysis by subgroup of participant gestational age. Statistical significance was set at p-value < 0.05 Results: The BD FACSPresto POC CD4 enumeration system showed similar performance with the other CD4+ T lymphocytes enumeration instruments. Strong correlations were obtained between the BD FACSPresto poc system and other single platform methods. Bland–Altman plots showed interchangeability between two machines mean bias BD-FACSPresto vs PIMA= -126,522(-161,221 to -91,822) BD-FACSPresto vs FACSCount= -38,708 (-58,935 to -18,482) and FACSPresto vs FACSCALIBUR= 0,791(-11,908 to 13,491). Mean difference with Absolute CD4+ T-lymphocyte values obtained from the BD FACSPresto system correlated well with PIMA, FACSCount, and FACSCalibur method with R² equal to 0.88, 0.92 and 0.968 respectively with P < 0.001 for all. The mean comparison between values obtained from BD FACSPresto with PIMA, FACSCount, and FACSCalibur using paired T test give P=0.17, P=0.5 and P=0.6 respectively meaning that there is no significant differences between values obtained with BD FACSPresto and PIMA, FACSCount or FACSCalibur CD4 enumeration machines. Further analysis revealed close agreement between all the three instruments with no significant difference between the four equipment with different methods of analysis (P=0.91) Conclusion: This BD-FACSPresto POC system is a simple, robust and reliable system for enumeration of absolute and CD4+ T-lymphocytes percentages especially in remote areas with limited resources. Having a single BD-FACSPresto POC system which is easy to use, should reduce the cost and thus increase and improved access to CD4 testing for HIV infected patients in remote areas of resource-constrained countries. BD-FACSPresto POC CD4 will enable reduction in patient wait time and improve the overall quality of ART service count and may improve test access in remote areas. This technology can allow for greater decentralization and wider access to CD4 testing in areas where viral load is not possible during ART