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What is the most accurate and cost effective method for measuring CD4 counts in HIV infected individuals living in resource-limited settings? Open Access

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Objectives: This study sought to describe the agreement of three alternative CD4 flow cytometers (BD FACSCount, Guava Technologies PCA/EasyCD4 system, and Partec CyFlow Counter) compared to the reference standard Becton Dickinson (BD) CD4 MultiTEST system run on the BD FACSCanto and BD FACSCalibur. These new instruments have far reaching public health implications and could prove to be a less expensive and more sustainable method for monitoring HIV positive patients in resource poor environments.Methods: A total of 303 delinked blood samples were collected. The samples were then subjected to parallel flow cytometric analysis on five separate flow platforms. The results were compared with the reference flow platform (FACSCanto); categorical analysis, univariate analysis, correlation analysis (r), and linear regression were calculated to detect any significant statistical differences between instruments. Then the mean differences (the estimated bias) were calculated and Bland-Altman plots generated. In addition, an ease of use survey was completed by each technician for each flow instrument. This data allowed the investigator to provide practical information beyond performance and cost.Results: These alternative technologies were evaluated for agreement (comparison with traditional methodology) by three different statistical methods. The CCC was utilized to determine the degree of agreement, taking into account both precision and accuracy, between the different cytometry methods. For this analysis, the CD4 counts estimated by the FACSCalibur and FACSCount showed high level agreement with the CD4 counts obtained by conventional flow cytometry. In addition, both instruments showed high sensitivity and specificity to identify patients with CD4 counts <=350 cells/ul. However, after including all data sets (extreme values and outliers), the Guava PCA (rho_c = 0.95) was more accurate than the FACSCount CD4 and CyFlow Counter in predicting FACSCanto CD4 count. Furthermore, the Guava PCA showed high specificity (99.1).Conclusion: These results, along with the other advantages of the Guava PCA, confirm that this simple-to-use, portable system can provide accurate CD4 test results and has the potential to provide improved access for patients to CD4 test results in even the most remote areas of the world, improving ongoing care for HIV/AIDS patients.

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