Single-platform, volumetric, CD45-assisted pan-leucogating flow cytometry for CD4 T lymphocytes monitoring of HIV infection according to the WHO recommendations for resource-constrained settings

Abstract

BackgroundValidation of new affordable CD4 T cell measurement technologies is crucial specifically in resource-poor countries for antiretroviral treatment eligibility and immunologic CD4 monitoring of HIV-infected patients.MethodsThe absolute and percentage CD4 T cell counts of 258 HIV-1-infected blood samples (182 adults and 76 children), living in N’Djamena, Chad, were performed by single-platform, volumetric, CD45-assisted pan-leucogating Auto40 flow cytometer (Apogee Flow Systems Ltd, Hemel Hempstead, UK) comparing to the FACSCalibur flow cytometer as a reference method.ResultsAbsolute and percentage CD4 T cell counts obtained by Auto40 and FACSCalibur of 258 HIV-1-infected blood samples were highly correlated (r = 0.99 and r = 0.96, respectively). The mean absolute bias and percent bias between Apogee Auto40 and FACSCalibur absolute CD4 T cell counts, were −9.4 cells/μl with limits of agreement from −15 to 93 cells/μl, and +2.0% with limits of agreement from −0.9 to 4.9%, respectively. The mean of absolute bias and percent bias between Apogee Auto40 and FACSCalibur of CD4 percentage results were +0.4% (95% CI: -0.02 – 0.86) with limits of agreement from −2.4 to 0.3%, and +3.0% with limits of agreement from −6.6 to 0.6%, respectively. The Auto40 counting allowed to identify the majority of adults with CD4 T cells below 200 cells/μl (sensitivity: 89%; specificity: 99%) or below 350 cells/μl (sensitivity: 94%; specificity:98%); and of children below 750 cells/μl (sensitivity: 99%; specificity: 96%) or below 25% CD4+ (sensitivity: 94%; specificity: 98%).ConclusionThe Auto40 analyzer is an alternative flow cytometer for CD4 T lymphocyte enumeration to be used in routine for immunological monitoring according to the current WHO recommendations in HIV-infected adults as well as children living in resource-constrained settings like Chad.

Field evaluation in Chad of community usage of CD4 T lymphocyte counting by alternative single-platform flow cytometry

“…The installation and extended usage of a significant number of Auto40 flow cytometers in Chad also allowed us to assess the performance of these CD4 T cells counters in situations of actual use, across an entire country with harsh climatic conditions and a large geographical territory. This field approach is original, and complements the previous strictly biological evaluations of the analyzers in reference laboratories in Senegal [ 11 ], Cameroon [ 21 , 22 ], as well as recently in Chad [ 23 ].…”

“…The CD45-assisted method for CD4 T cells enumeration in percentage has been previously demonstrated to allow accurate CD4 T cell counting, when used in dual [ 15 - 17 ] as well as single-platforms, either volumetric [ 18 ] or bead-based [ 19 , 20 ]. The updated version of the Auto40 analyzer has been recently validated for the enumeration of both absolute numbers and percentages of CD4 T cells in Cameroon [ 21 , 22 ] as well as in Chad [ 23 ] and is therefore addressing the current WHO recommendations for CD4 T cell measurements in children less than 5 years [ 5 ].…”

“…Indeed, the conditions within many community laboratories, where several Auto40 analyzers have been implemented, are not similar to the conditions within the laboratories in large cities and academic medical centers where the Auto40 flow cytometer has been previously evaluated. Such evaluations have occurred in laboratories in Dakar, Senegal [ 11 ], Yaoundé, Cameroon [ 21 , 22 ] and Chad [ 23 ]. Furthermore, Chad is a country with particularly difficult conditions in terms of both climate and bad infrastructures making the decentralization of the therapeutic management of HIV-infected patients especially challenging.…”