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Objective: The HIV pandemic remains a significant global health concern. Accurate determination of CD4+ T-cells in patient samples relies on reliable CD4 enumeration. The Quality Assessment and Standardization programme for Immunological measures relevant to HIV/AIDS (QASI) programme of the Public Health Agency of Canada provides clinical laboratories from resource-limited countries with a mechanism to evaluate the quality of CD4 testing and develop the implementation of an independent national External Quality Assessment (EQA) programme. This study describes how QASI helped develop the capacity for managing a sustainable national CD4 EQA programme in India.Design: Supported by the Public Health Agency of Canada and Clinton Foundation HIV/AIDS Initiative, QASI engaged with the National AIDS Control Organization and the Indian National AIDS Research Institute to assist in technology transfer in preparation for the implementation/ management of an independent CD4 EQA programme. Technology transfer training was provided to support corrective actions and to improve the quality of CD4 testing. Inter- laboratory variation of EQA surveys between pre- and post-skill development was compared.Results: Prior to training, coefficient of variation values were 14.7% (mid-level CD4 count controls) and 39.0% (low-level). Following training, variation was reduced to 10.3% for mid- level controls and 20.0% for low-level controls.Conclusion: This training assisted the National AIDS Control Organization and the Indian National AIDS Research Institute in identifying the information necessary for management of an EQA programme, and developed the foundation for India to provide corrective actions for sites with challenges in achieving reliable results for CD4 enumeration. This led to a demonstrable improvement in CD4 testing quality and illustrates how country-specific training significantly improved CD4 enumeration performance for better clinical management of HIV care in India.

Background The global HIV/AIDS pandemic and guidelines for initiating anti-retroviral therapy (ART) and opportunistic infection prophylaxis demand affordable, reliable, and accurate CD4 testing. A simple innovative approach applicable to existing technology that has been successfully applied in resource-challenged settings, PanLeukogated CD4 (PLG), could offer solutions for cost saving and improved precision. Methods Day-old whole blood from 99 HIV+ donors was simultaneously studied in five North-American laboratories to compare the performance of their predicate methods with the dual-platform PLG method. The predicate technology included varying 4-color CD45/CD3/CD4/CD8 protocols on different flow cytometers. Each laboratory also assayed eight replicate specimens of day-old blood from 10 to 14 local donors. Bias and precision of predicate and PLG methods was studied between- and within-participating laboratories. Results Significantly (P < 0.0001) improved between-laboratory precision/coefficient of variation (CV%) was noted using the PLG method (overall median 9.3% vs. predicate median CV 13.1%). Within-laboratory precision was also significantly (P < 0.0001) better overall using PLG (median 4.6% vs. predicate median CV 6.2%) and in 3 of the 5 laboratories. PLG counts tended to be 11% smaller than predicate methods (P < 0.0001) for shipped (median of predicate—PLG = 31) and local specimens (median of predicate—PLG = 23), both overall and in 4 of 5 laboratories (median decreases of 4, 16, 20, and 21% in shipped specimens); the other laboratory had a median increase of 5%. Conclusion Laboratories using predicate CD4 methods similar to those in this study could improve their between-laboratory and their within-laboratory precision, and reduce costs, by switching to the PLG method after adequate training, if a change (usually, a decrease) in CD4 counts is acceptable to their health systems. © 2008 Clinical Cytometry Society

Background The global struggle with human immunodeficiency virus (HIV) and the battle to develop affordable CD4 T-cell counting technology are both unfulfilled goals in 2008. The need for such instrumentation is more critical now as implementation of antiretroviral therapy (ART) is in progress in many resource limited regions. Major scaling-up efforts in rural situations are difficult to implement without laboratory infrastructure. CD4 T-cell counting is especially critical when trying to reach individuals with HIV to have them enrolled in ART as soon as they qualify for treatment based on CD4 count. Method This review covers both the chronological evolution and the scientific milestones of technological development of affordable immunophenotyping. It is more focused on flow cytometry but does consider the potential contribution by digital image cytometry. Results Thus far flow cytometry offered only modest progress toward affordable immunophenotyping. A list with desirable features is offered for side by side comparison. Digital image cytometry has yet to show its enormous affordable market potential. Conclusions It is possible to develop truly affordable, portable flow cytometry but it is not here yet. There are some hopeful signs as there are innovative and practical technical components appearing at regular intervals. However, so far the technical breakthroughs have been fragmented efforts without any attempts to consider intercorporate collaboration to optimize critical mass and synergy. The smaller players in the industry have made some progress toward meeting the monumental needs in Africa and Asia. Digital image cytometry may well be the ultimate winner in the affordable technology race. © 2008 Clinical Cytometry Society

Background: A new generation of bench-top flow cytometers with digital signal processing to perform suspension array technology (SAT) based bead array assays as well as leukocyte immunophenotyping is now available. These hybrid instruments provide an opportunity for the development of a more cost effective multitasking platform to support infectious disease treatment in resource limited countries. Methods: We report the development and testing of two modules compatible with the hybrid flow cytometers. The first module is an eleven HIV-1 protein bead array (PBA) for the detection of circulating antibodies and the second is a cell based T-cell enumeration assay. Results: The HIV-1 PBA was tested in parallel with two enzyme immunoassays (EIAs) for the detection of plasma antibodies from 4 HIV-1 seroconversion panels and a low antibody titer panel. The PBA as well as the two EIAs performed equally for the detection of antibody positive samples from all seroconversion panels. One antibody positive sample from the low antibody titer panel was missed by the PBA together with one of the two EIAs tested. A parallel analysis of the HIV-1 PBA with Western blot (a confirmatory test for HIV infection) using plasma from nine HIV-1+ individuals showed that the HIV-1 PBA detected more of the gp41 and gp120 antibody positive samples. Preliminary CD4 T-cell immunophenotyping results from 14 HIV+ and 10 HIV− whole blood specimens with the hybrid flow cytometer platform compared well to conventional flow cytometry data. Conclusion: The successful combination of bead and cell based assays on a single hybrid instrument demonstrated the potential utility of a multitasking platform. The results presented are providing groundwork for future development of more cost effective modular architecture for a flexible flow cytometry based platform. © 2006 International Society for Analytical Cytology

Background: Exceptionally robust cell preparations are needed for quality assessment programs (QAPs) such as the International Program for Quality Assessment and Standardization for Immunological Measures (QASI) relevant to HIV/AIDS. A suitable product must withstand environmental stress related to transportation for a minimum of 6 days. The two objectives of this study are (1) to evaluate the performance of various commercial preparations with multicenter participation and (2) to evaluate the robustness of stabilized blood cell products. Methods: Phase 1: The performance of stabilized blood cell products was evaluated in a multicenter QAP utilizing various staining procedures and flow cytometers. Absolute cell enumeration was achieved using single-platform T-cell subset methodology. Phase 2: The robustness of stabilized blood cell products was evaluated by monitoring T-cell subset values from samples stored at 4°C, 22°C, and 37°C for up to 10 days. Results: The largest interlaboratory variation in both absolute and relative T-cell values was 16% in samples with CD4 levels >400 cells per microliter and 21% in samples with CD4 levels

Measurements of CD4 T-cell levels are essential for the assessment of human immunodeficiency virus (HIV) disease course, clinical staging, epidemiological studies, and decisions regarding prophylactic therapies against opportunistic infection. Until now, only in the industrialized countries was T-cell subset monitoring considered a practical option to assess disease progression. The Quality Assessment and Standardization for Immunological Measures Relevant to HIV/AIDS (QASI) program was established in 1997 to meet performance assessment for immunophenotyping laboratories in countries where such service is not available. The QASI program is provided at no cost to any laboratory in a resource-poor setting that wishes to participate. This report describes the beneficial impact of participation in the QASI program. Carefully selected commercial stabilized whole blood preparations were sent regularly to participating laboratories. Participants reported the T-cell subset values they obtained by flow cytometry. Once the aggregate mean values for the T-cell subsets were established for the shipment, a comprehensive and confidential report was sent to each laboratory. The results from five consecutive shipments were analyzed. The coefficient of variation decreased from 7.2% to 4.7% and from 14.2% to 8.8% for percent and absolute CD4 T-cell counts, respectively. With the implementation of the QASI program using commercial stabilized whole blood specimens, it is possible to reduce interlaboratory error. This study illustrates that a quality assessment program can improve the overall performance of laboratories. Reducing interlaboratory variation can enhance significantly the effectiveness of multicenter HIV vaccine or drug trial evaluation.

BACKGROUND In the past decade, human immunodeficiency virus (HIV) lymphocyte immunophenotyping has evolved significantly. New fluorochromes, new multicolor reagents, enhanced instruments, and the capacity to provide absolute cell counts using the single-platform technique have all contributed to the reliability of T-cell subset measurements. In this study, four gating protocols were evaluated to select the most robust method for T-cell subset enumeration. Methods: Peripheral blood specimens from 21 HIV+ and 20 HIV− individuals were monitored up to 96 h. Aliquots of specimens were stored at room temperature and analyzed at 6 (baseline), 48, 72, and 96 h. Aliquots were stained with CD45-fluorescein isothiocyanate (FITC)/CD3PC5/CD4RD1/CD8ECD. Data analysis was performed with all four gating protocols. Results: Only with fresh blood did all protocols provide similar results. From samples that were 48 h old, the choice of gating strategy had a dramatic impact on immunophenotyping results. The largest deviations from baseline values occurred at 96 h and gating protocols that included dual light scatter gates provided the greatest shift of T-cell subset values over time. The gating protocols that were based exclusively on cell lineage-specific gates gave the most robust T-cell values up to 96 h. Conclusion: By selecting the appropriate gating protocol, the temporal integrity of specimens can be extended up to 4 days. Cytometry (Clin. Cytometry) 50:53–61, 2002. © 2002 Wiley-Liss, Inc.

This brief review of the development of gating strategies for CD4 1 T-cell enumeration is really the story of contemporary clinical flow cytometry. It is the chronicle of its birth, and its slow invasion into the clinical immunology laboratory over the past 15 years. The driving force behind the technological evolution of leukocyte immunophenotyping was, and still is, the impact of the HIV/AIDS pandemic on the discipline of immunology. While, at times, this review of analytical flow cytometry makes metaphorical excursions into the literary world, the objective is not to trivialize technology. Rather, it attempts to illustrate how, in his drive to solve the practical problems of modern medicine, man’s essentially eclectic nature excels in an environment of diverse knowledge. This review will examine how technological advancements, such as the introduction of clinical instruments with multi-color capabilities, and the evolution of leukocyte gating strategies, has influenced the evolution of leukocyte immunophenotyping. Cytometry 30:157‐165, 1997. r 1997 Wiley-Liss, Inc. Key terms: immunology; metaphor; multi-color capabilities In his metaphorical essay, ‘‘Godel, Escher, Bach: An Eternal Golden Braid’’ (1), Pulitzer Prize winner Douglas Hofstadter exemplified the impact of great trilogies on humanity by weaving the contributions of three universal giants into a unified concept. The impact of Hofstadter’s trilogy far outweighs the impact generated by the emergence of leukocyte immunophenotyping, but it does serve as a compelling example of how disciplines which are conceptually far apart can still fuse and consolidate knowledge. Contemporary clinical flow cytometry also required the unifying force of several powerful trilogies. The events that would culminate in the birth of the current state-of-the-art flow cytometry were initiated in three different countries and were based on three fundamentals derived from as many different scientific disciplines. The first essential step in the development of present-day analytical cytology dates back to nineteenth century Germany, where Paul Ehrlich first described the fundamental extrinsic properties of leukocytes (2). The second important step took place in Stockholm during the 1930’s, where Caspersson and his colleagues unraveled some of the crucial elements of modern analytical cytology. In the course of making some precise microspecrophotometric absorption measurements of unstained cells, they defined some of the essential intrinsic properties of leukocytes (3). In Boston, during the early 1940’s, Coons, Creech, and Jones developed a cell labeling technology for microscopy which enabled researchers to detect fluorescent antibodies bound to cell surface epitopes (4). Their qualitative measurement of extrinsic properties of cells was the third essential step leading to modern immunophenotyping of leukocytes (5).

Background: Efforts to improve alternative CD4 T-cell counting methods are critical to accelerate the implementation of HIV antiretroviral therapy in resources limited regions. Substituting liquid format reagents to eliminate cold-chain transportation and refrigerated storage with dry format reagents contributes to higher efficiency supply management solution especially for laboratories at remote locations. ReaMetrix has developed dry format reagent kits compatible with the FACSCount system, a dedicated flow cytometer for T-cell subset enumeration widely used in resource limited settings. A dual site collaborative study was designed to compare T-cell subsets using both the new dry format ReaMetrix reagent and the original BD Biosciences liquid reagents. Method: A total of 167 HIV positive samples prepared with Rea T Count (ReaMetrix) and FACSCount (BD Biosciences) reagents were analyzed using FACSCount Systems. To compare both methods, Bland-Altman, Pollock, Scott % similarity and correlation coefficient statistical analysis was applied. Immuno-Trol served as an assay processing control and quality indicator of interlaboratory and intralaboratory variation. Results: The mean bias and limits of agreement for CD4 T-cell measurements between Rea T Count and FACSCount reagents were −16 cells/μl (−4.6%) and −74 to +43, respectively. The correlation obtained was 0.988 with a similarity of 97.9%. Between laboratory variation data was very good with %CV below 10%. Conclusion: The introduction of dry reagents permits the elimination of cold-chain transportation and the on-site refrigerated storage without compromise to assay quality. The substitution of dry reagents facilitates easier supply management practice that will assure wider access to quality HIV treatment. © 2009 Clinical Cytometry Society

M. Bergeron, G. Lustyik, S. Phaneuf, T. Ding, J. K. A. Nicholson, G. Janossy, H. Shapiro, D. Barnett, and F. Mandy* Health Canada, Ottawa, Ontario, Canada Soft Flow, Inc., Minneapolis, Minnesota National Center for Infectious Diseases, Atlanta, Georgia Royal Free and University College Medical School, London, United Kingdom West Newton, Massachusetts Royal Hallamshire Hospital, Sheffield, United Kingdom

The single-platform absolute T-lymphocyte subset analysis was evaluated utilizing a universal protocol in a Canadian multicenter study with the collaboration of the members of the Canadian HIV Trials Network (CTN). Participants used flow cytometers and reagents of their choice for labeling and lysing whole blood. Over a 2-year period, CTN laboratories performed single-platform absolute T-lymphocyte subset enumerations on fresh and commercial stabilized blood products using commercially available microfluorospheres TruCount and Flow-Count. This multicenter evaluation demonstrated that the application of a universal template for single-platform analysis provides a generic approach that embraces a wide array of immunophenotyping settings available in clinical laboratory.