CD4 +T lymphocytes are the main infected targets of the Human Immunodeficiency Virus (HIV) in bodies. CD4 level will gradually decrease in HIV hosts when their immune systems are becoming more and more weak, which finally causes Acquired Immune Deficiency Syndrome (AIDS). Therefore, the number of CD4 +T lymphocytes for HIV hosts at different stages is critical to the diagnosis and therapy of HIV/AIDS. For example, Antiretroviral therapy (ART) normally requires four periodical CD4 +T tests in one year for clinical diagnosis and treatment. Population with HIV/AIDS is increasing significantly all over the world in the past ten years. The existing methods for CD4 +T lymphocyte counting are unavailable to developing countries or undeveloped areas because of expensive devices, complicated procedures and high cost. To solve this problem, based on microfluidic technology, new CD4 +T lymphocyte counting methods are being intensively studied for low cost, rapid and convenient CD4 +T lymphocyte detection in the point-of-care test (POCT). After a brief introduction on traditional methods, this paper reviews and summarizes CD4 +T lymphocyte counting methods based on microfluidic chips. The typical technical characteristics of chip-based CD4 +T lymphocyte counting methods are identified and grouped, and furthermore, their general performance, application area, and major advantages with disadvantages are discussed and evaluated in details. Finally, an outlook and conclusion for research, development and commercialization of CD4 +T lymphocyte counting based on microfluidic chip are given after a detailed discussion.

Contents
1 Introduction
2 Clinical value and classification of CD4 +T counting 2.1 Clinical value of CD4 +T counting
2.2 CD4 +T counting with flow cytometry
2.3 CD4 +T counting with manual operation
2.4 CD4 +T counting with microfluidic chip
3 CD4 +T counting based on single cell detection with microfluidic chip
3.1 CD4 +T counting based on cell image
3.2 CD4 +T counting based on optical or electrical signal of single cell
4 CD4 +T counting based on the macro-characteristics of cell group with microfluidic chip
4.1 CD4 +T counting based on chemiluminescence of cell group
4.2 CD4 +T counting based on impedance of cell group
4.3 CD4 +T counting based on the macro-physical characteristics of cell group
5 Conclusion and outlook