Low-Cost CD4 and CD8 Tests for HIV/AIDS

Low-Cost CD4 and CD8 Tests for HIV/AIDS

Results of a multisite study of two new low-cost tests for the enumeration of CD4+T cells and CD8+T cells show excellent correlation with the standard flow cytometry assay. The findings were presented at the 15th International AIDS Conference in Bangkok (Thailand) in July 2004.

The investigators collected blood samples from volunteers and delivered them to each of the participating laboratories within four hours. Each site tested each specimen by the EasyCD4 and EasyCd8 methods in triplicate. In addition, a tube of matched blood was analyzed by the predicate BD MultiTEST (Becton Dickinson) method at the University of California, San Francisco, Clinical Laboratory (UCSF, USA). In addition to the excellent correla­tion with the standard, assay reproducibility both within site and between sites was excellent.

Absolute CD4+ and CD8+ T cell counts are used to monitor disease progression in HIV/AIDS patients, to determine when to begin treatment with anti-retroviral drugs, and to monitor a patients response to treatment. In resource-limited countries, the cost of commercially available CD4 diagnostic testing has remained high. The new tests, from Guava Technologies, Inc. (Hayward, CA, USA; www.guavatechnologies.com), offer affordability that could potentially enable improvements in the quality of care and life for the millions of HIV patients these countries.

“With many resource-limited areas of the world now gaining access to more affordable antiretroviral therapies, simpler and less costly methods of monitoring treatment – including absolute CD4+ and CD8+ T cell counts – are urgently needed,” said Barry Bredt, Ph.D., one of the researchers and director of core laborato­ries, General Clinical Research Center, UCSF/San Francisco General Hospital. “The Guava assays offer comparable accuracy and reproducibility to the flow cytometer method, but are much simpler and more affordable to use.”

Guava’s EasyCD4 and EasyCD8 assays represent an optimized, integrated system of reagents, software, and instrumentation. The company’s microcapillary cytometry technology enables the instrument to be highly compact, portable, and needing little maintenance. Operation of the assays is simple, with even novice users learning to use the tests in less than a day. Testing requires only 10 microliters of whole blood per patient, making the method suitable for children as well as adults. The cost per test is U.S.$1.25 – 4.00, compared to $3-20 for flow cytom­etry tests.

Since the assays require far less reagent per sample, the cost of performing the assay is dramatically lowered. Moreover, the assays do not require a dedicated laboratory infrastructure or large amounts of buffered water as sheath fluid, which are required by conventional flow cytometers. The elimination of the use of sheath fluid also results in less biohazardous waste and further reduces the cost of running the sys­tem.

Guava is currently marketing the EasyCD4 and EasyCD8 in countries out-side the United States, Europe, and Japan. The company is seeking clearance of the EasyCD4 system in the United States as a clinical diagnostic product.

Image: The Easy CD4 assay system (Photo courtesy of Guava Technologies).