CD4+ T lymphocytes enumeration by an easy- to-use single platform image cytometer for HIV monitoring in resource-constrained settings

Abstract

Background: HIV monitoring in resource-constrained settings demands affordable and reliable CD4+ T lymphocytes enumeration methods. We developed a simple single platform image cytometer (SP ICM), which is a dedicated volumetric CD4+ T lymphocytes enumeration system that uses immunomagnetic and immunofluorescent technologies. The instrument was designed to be a low-cost, yet reliable and robust one. In this article we test the instrument and the immunochemical procedures used on blood from HIV negative and HIV positive patients. Methods: After CD4 immunomagnetic labeling in whole blood, CD4+ T lymphocytes, CD4+dim monocytes and some nonspecifically labeled cells are magnetically attracted to an analysis surface. Combining with CD3-Phycoerythrin (PE) labeling, only CD3+CD4 + T lymphocytes are fluorescently labeled and visible in a fluorescent image of the analysis surface. The number of CD4+ T lymphocytes is obtained by image analysis. Alternatively, CD3 immunomagnetic selection in combination with CD4 immunofluorescent labeling can also be applied for CD4+ T lymphocytes enumeration. Results: The SP ICM system was compared with two single platform flow cytometer (SP FCM) methods: tetraCXP and TruCount methods. The SP ICM system has excellent precision, accuracy and linearity for CD4+ T lymphocytes enumeration. Good correlations were obtained between the SP ICM and the SP FCM methods for blood specimens of 44 HIV- patients, and of 63 HIV+ patients. Bland-Altman plots showed interchangeability between the SP ICM and the SP FCM methods. Conclusions: The immunolabeling methods and the instrumentation are simple and easy-to-handle for less-trained operators. The SP ICM system is a good candidate for CD4+ T lymphocytes enumeration in point-of-care settings of resource-constrained countries. © 2007 Clinical Cytometry Society.