New lower-cost assay system equivalent to flow cytometry for accurate CD4+/CD8+ cell counts


Guava EasyCD4+ may increase global access to affordable, easy HIV/AIDS patient monitoring

HAYWARD, CA (July 12, 2004): Results from a multi-site study evaluating two new assays from Guava Technologies, Inc. that dramatically lower the cost and difficulty of AIDS diagnosis and treatment monitoring were presented Sunday at the 15th International AIDS Conference, held July 11 17 in Bangkok, Thailand. Data from three separate study sites showed that results obtained using the Guava EasyCD4 and EasyCD8 Assays for the enumeration of Human CD4+ T cells and CD8+ T cells showed excellent correlation with the standard, clinically approved BD MultiTESTTM (flow cytometry) assay. Moreover, assay reproducibility both within-site and between-sites for the Guava assays was excellent.

Study results were provided by investigators from the University of California, San Francisco (UCSF), the Gladstone Institute of Virology and Immunology, California Department of Health Services, and Guava Technologies, Inc. They were presented at the satellite symposium organized by the Forum for Collaborative HIV Research and entitled "HIV Monitoring Technologies for Resource-Limited Settings."

"With many resource-limited areas of the world now gaining access to more affordable anti-retroviral 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., director of core laboratories, General Clinical Research Center, UCSF/San Francisco General Hospital. "Our results suggest that the EasyCD4 and EasyCD8 assays represent good lower cost alternatives to approved flow cytometry methods of CD4+ and CD8+ T cell enumeration. The Guava assays offer comparable accuracy and reproducibility to the flow cytometry-based method, but are much simpler and more affordable to use."

Absolute CD4+ and CD8+ T cell counts are measurements used to monitor disease progression in HIV/AIDS patients, to determine when to begin treatment with antiretroviral drugs and to monitor a patient's response to treatment. In resource limited countries, the cost of commercially available CD4 diagnostic testing, whether by "gold standard" flow cytometry or less accurate manual microscopy-based methods, has remained very high. The Guava EasyCD4 system can dramatically change that and potentially enable improvements in quality of care and even quality of life for the millions of HIV+ patients in these countries.

Study Design and Results

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 MultiTESTTM method at the UCSF Clinical Laboratory.

A plot of percent difference between EasyCD4 and EasyCD8 methods and the MultiTEST method showed no trends in bias across the observed range. The median percent differences for the three sites ranged for CD4 from 1.8% to 8.3% and CD8 from 13.1% to 8.6%. Similarly the median between-site variability of the EasyCD4 and EasyCD8 was calculated to be 10.6% and 10.8% respectively. To estimate within-site variability, %CVs (coefficient of variation) were calculated using the three EasyCD4 and EasyCD8 replicates at each site and were reported to be 4.1% to 5.6% and 4.5 % to 5.1%, respectively.

Correlation of both the EasyCD4 and EasyCD8 assays with the BD MultiTEST assay and inter- and intra-site reproducibility were excellent. A small negative bias ('10%) between the EasyCD8 and BD MultiTEST assay was observed.

Guava Technologies provided financial support for the study.

About the Guava EasyCD4

The Guava EasyCD4 and EasyCD8 represent an optimized, integrated system of reagents, software and instrumentation. Guava Technologies' microcapillary cytometry technology enables the instrument to be highly compact, portable and low maintenance. Operation of the Guava assays is quite simple, with even novice users learning to use the EasyCD4 and EasyCD8 in less than a day. Testing requires only 10 microliters of whole blood per patient, making the method suitable for use in pediatric as well as adult patients. The Guava EasyCD4 assay also requires far less reagent per sample, dramatically lowering the overall costs of performing the assay. Moreover, the Guava EasyCD4 and EasyCD8 do not require the dedicated laboratory infrastructure or large amounts of buffered water as sheath fluid that are required by conventional flow cytometers. The elimination of the use of sheath fluid also results in less bio-hazardous waste and further reduces the running costs of using the system. Daily maintenance is minimal just a fast and easy 5 minute clean and shutdown procedure performed at the end of each day.

"The Guava EasyCD4 and EasyCD8 enable easy monitoring of T cell health in HIV-infected patients, using a benchtop system that is reliable and robust, and that provides results with excellent precision and accuracy," said Rajen Dalal, chief executive officer of Guava Technologies. "Moreover, EasyCD4 and EasyCD8 dramatically lower the cost of testing, from the $3 to $20 per test using flow cytometry-based methods to $1.25 to $4.00 per test using the Guava assays."

Guava is currently marketing the EasyCD4 and EasyCD8 in nations outside of the United States, Europe and Japan. The company is also introducing a version of the EasyCD4 system for research use only in the United States and will subsequently seek U.S. Food and Drug Administration clearance for use of the system as a clinical diagnostic product.

About Guava Technologies

Guava Technologies, Inc. is a leading provider of integrated, fully optimized microcapillary cytometry systems for many of the most important cell analysis applications. Guava's initial focus has been to serve the worldwide life science, biotechnology and pharmaceutical industries, offering a state-of-the-art, comprehensive portfolio of products designed to accelerate discovery and increase productivity with accessible, easy-to-use solutions for the biologist's testing problems, available right at the lab bench. Guava's products have broad applications in scientific research, drug discovery, cell counting, and optimization of commercial bio-production. The introduction of Guava's technology platform for clinical diagnostic use begins with the CD4/CD8 assays for HIV/AIDS monitoring in developing countries. There is also enormous potential for other uses in clinical testing and blood processing and indeed any area where single cell counting and characterization is important.

The Guava PCA systems offer an integrated, optimized approach that takes the guesswork out of single cell analysis and counting. Based on patented microcapillary cytometry technology, the Guava PCA systems are available in several versions, to exactly meet the needs that exist in different laboratories. These cell analysis systems are flexible, highly affordable and ultra-compact, requiring only a few microliters of sample volume per assay, thus saving precious and expensive cells, reagents and compounds. Guava offers a variety of assays and dedicated software modules for the Guava PCA systems, enhancing the system's overall ease-of-use.

More information about the company and its products is available at

Guava and Guava Technologies, Inc. are registered trademarks of Guava Technologies, Inc. PCA and PCA-96 are trademarks of Guava Technologies, Inc. BD MultiTEST is a registered trademark of BD Biosciences.

Source: Eurekalert & others

Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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