Preclinical Assessment of a Cartridge-Based Flow-Through Assay for Determination of Adult CD4 T-Cell Count

Despite the emphasis on viral load testing, current HIV testing guidelines consider CD4 T-cell count measurement as an important criterion for assessing disease progression, making decisions about anti-retroviral therapy regime changes, and treating HIV infected individuals with opportunistic infections. The CD4 counting by established methods (e.g., flow cytometry) presents challenges not only in resource-scarce settings due to cost and lack of skilled technicians but also in resource-rich areas where it is limited to centralized facilities.

Current options for Point-Of-Care (POC) CD4 enumeration are few and labor-intensive, prompting the need for newer technological methods that can overcome the aforementioned challenges.

The novel and patented flow-through cell counting assay (FTCA) described previously (Bystryak et al., 2019) was developed further into a point-of-care CD4 testing system using a disposable cartridge device and a portable imaging instrument. A pilot study with ~100 samples using this device was conducted to assess the validity of FTCA as a POC test for the measurement of CD4 count.

The FTCA signal was found to be linear over a wide range (17 - 1540 cells/μL) of CD4 T-cell concentration. The FTCA method also exhibits a strong agreement with flow cytometry, with very low bias (− 7 cells/μL) towards CD4 count measurement.

The cartridge-based FTCA method has great potential to be a fully quantitative method with low complexity, portability, low-cost, and wide applicability in clinical practice.