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.
Highlights
Validation of new affordable CD4 T cell measurement technologies is crucial in resourcepoor countries for antiretroviral treatment eligibility and immunologic CD4 monitoring of HIV-infected patients
Accuracy of direct volumetric CD4 T cell measurements by the Auto40 flow cytometer in Chad A total of 258 EDTA-blood samples with correct preanalytical preparation were obtained from 182 HIV-1infected adults, and 76 HIV-1-infected children older than 5 years
The majority of study patients (74%) were taking antiretroviral therapy (ART) according to the World Health Organization (WHO) recommendations for resourcelimited settings, whereas 26% of them were naïve for ART
Summary
Validation of new affordable CD4 T cell measurement technologies is crucial in resourcepoor countries for antiretroviral treatment eligibility and immunologic CD4 monitoring of HIV-infected patients. Recent studies have demonstrated that POC CD4 T lymphocytes monitoring can significantly improve rates of ART initiation and reduce patient loss-to-follow-up, which is often high before treatment initiation [1,8,9]. Affordable CD4 T cell counting has gradually become possible by using simple, compact and robust low-cost new generation of POC flow cytometers operating as single-platform volumetric instruments without the use of expensive microbeads [7,12,13,14]. Its absolute volumetric counting allows the direct determination of the number of cells per unit of sample volume without the need for reference material such as microbeads [13,18]
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