###### Abstract
Notably, PIMA has been reported in numerous studies to have high homology with the standard FACS methods and can thus be a candidate for alternative CD4 counting [13; 14]. However, these instruments and their accompanying non-recyclable materials are still expensive compared with the affordability of medical sectors with limited resources, mostly because of optic combined fluidic technology, which requires quality control of all parts, calibration, and stringent reagent and test components during storage, which may be interrupted, as indicated by error codes [15]. Over time, one of these parts can be damaged and require replacement [16], consequently increasing the test costs. Another technology, magnetic-activated cell sorting (MACS), is an alternative and simple approach for the development of CD4\({}^{+}\) T cell counting devices. The mechanism by which MACS separates the target cells of interest resembles FACS in that it uses antibodies (Ab), which can recognize cell surface markers, but these are alternatively conjugated to magnetic particles (MPs) rather than to fluorescent dyes; magnetically labeled cells are then sorted using an external magnetic field. Using specific antigen-antibody recognition, MPs can be applied to separate a wide range of immune cell types once conjugated with Abs. For example, MPs conjugated with EpCAM antibody or anti-HER2 are used to separate rare cancer cells [17; 18]; MPs conjugated with protein A are used for separation of monocytes and B-Lymphocytes [19] from blood samples, and anti-Salmonella-labeled MPs can be used to isolate harmful bacteria from food products [20]. Currently, there are many commercially available kits for the specific purification of CD4\({}^{+}\) T cells. Typically, as illustrated by the Anti-Human CD4 Particles kit (BD Bioscience), CD4\({}^{+}\) T cells are purified through a 2-step approach: first, about 2-4 mL of blood input is first pre-separated by sucrose-gradient centrifugation on a swing-out centrifuge to obtain peripheral blood mononuclear cells (PBMCs); CD4\({}^{+}\) T cells are then specifically captured by anti-CD4 conjugated nanoparticles (NP-CD4), and then separated using a magnet. Another kit enables CD4\({}^{+}\) T cell separation using combined streptavidin-conjugated particles and anti CD4-biotin (Dynabeads\({}^{\circledR}\)FlowComp\({}^{\circledR}\) Human CD4, Invitrogen, Waltham, MA, USA): first, CD4-Biotin is incubated with 2 mL blood samples. Next, the cell sample is subjected to a short centrifugation so that cells can precipitate to the bottom of the sample tube, and excessive antibodies are removed after discarding the supernatant. Magnetic particles conjugated with streptavidin (MP-streptavidin) are then incubated with the sample to allow interaction of streptavidin and biotin. Finally, the MP-strep-bio-CD4 cell complexes are separated using a magnetic field. This format was used by [PERSON] et al. for the semi-quantification of CD4\({}^{+}\) T cells [21]. Magnetic-based cell separation systems have a simpler format compared with fluorescence-based methods, but the greatest obstacle preventing MACS to be applied in diagnostics is its fluctuating cell separation efficiency, followed by labor-extensive procedures. Despite being introduced as early as the nineteenth century [22], the application of MACS in diagnosis has still been limited. The main reason for this is that cells must be separated with stable efficiency so that the original cell counts can be calculated. In addition, the aforementioned procedure for cell separation remains complicated and/or requires a large sample input. In an attempt to reduce the gap between MACS utilization and CD4\({}^{+}\) T cell counting applications, we developed a CD4\({}^{+}\) T cell counting system based on a simple MACS-separation for CD4\({}^{+}\) T cells using a small blood input required, followed by automated cell counting.