Point-of-Care CD4 Counter Evaluated

The measurement of the absolute CD4 T-cell count is critical in the initial evaluation and staging of persons infected human immunodeficiency virus (HIV).

However, access to the technology that allows for such measurements remains limited in many low resource settings where disease burden of HIV and acquired immunodeficiency disease syndrome (AIDS) is highest.

Scientists at MBio Diagnostics (Boulder, CO, USA) working with colleagues at the University of California (San Diego, CA, USA) evaluated the performance of a prototype point-of-care device (POC) to quantify CD4 T cells. The device combines single-use, disposable cartridges with a simple reader instrument. Based on the principle of static imaging cytometry with fluorescent immunostaining, the system utilizes a novel, laser-based illumination approach combined with MBio's proprietary planar waveguide technology.

A total of 94 participants provided venous whole blood samples and 52 capillary whole blood specimens. Study participants were HIV-infected individuals enrolled through a large primary HIV care program, at the University of California, San Diego between May 2011 and October 2011. Participants were predominantly male, of Caucasian and Hispanic race/ethnicity, with a median age of 44 years. The device, known as the Snapcount system, is a product of MBio Diagnostics and was compared with conventional flow cytometry (FACSCalibur, Becton Dickinson).

The prototype MBio system showed negligible quantitative bias relative to flow cytometry. Higher variability was observed in the capillary samples relative to venipuncture, but system precision was good for both capillary and venipuncture samples. There was also close agreement between results from the same participant when tested with two different systems, different operators, and different locations.

The authors wrote that developmental efforts are underway on a cartridge that incorporate lyophilized reagents and allows direct whole blood addition combined with a reader device. The reader device would include an integrated touch screen, internal and external quality control features, and data management software and network connectivity. The study was published in the January 2013 edition of the Journal of Immunological Methods.


Related Links:
MBio Diagnostics
University of California San Diego
Becton Dickinson