MONTREAL, Feb. 10 /PRNewswire-FirstCall/ -- As genetically divergent strains of the HIV virus become increasingly prevalent in the United States, the ability of clinicians to effectively monitor progress of anti-viral drug therapies depends on the capacity of viral load assays to accurately quantitate, or measure, these variant HIV strains, according to research reported today at the 16th Conference on Retroviruses and Opportunistic Infections (CROI).
A study by the Global HIV Surveillance Program at Abbott showed significant variation in the ability of diagnostic tests to accurately monitor viral load in patients infected with differing strains, or subtypes, of the HIV virus. The study evaluated HIV-infected specimens using the Abbott RealTime HIV-1 test and the Roche COBAS Taqman HIV-1 test.
According to the study, the Abbott RealTime HIV assay quantitated HIV more accurately than the widely used COBAS Taqman assay in an analysis of 317 seropositive samples from seven countries: Argentina, Brazil, Cameroon, Saudi Arabia, South Africa, Thailand and Uganda. The samples included six different HIV subtypes and eight circulating recombinant forms. Only 18 samples were subtype B, the most common HIV strain in the United States.
The research showed the Taqman assay failed to detect five infected samples and underquantified viral load in 38 samples, compared to the Abbott assay.
“The differences in viral load quantitation between assays is likely due to the impact of HIV genetic variation on assay performance,” said John Hackett, Ph.D., lead author from the Abbott HIV Global Surveillance Program. “Since viral load measurement is critical for optimal patient management, clinicians must recognize that HIV diversity can influence the accuracy and reliability of assay performance.”
The Abbott RealTime HIV-1 test is used in conjunction with clinical presentation and other laboratory markers as an indicator of disease prognosis, and as an aid in assessing viral response to antiretroviral treatment as measured by changes in plasma HIV-1 RNA levels. The RealTime assay is not intended for use as a donor-screening test for HIV-1 or as a diagnostic test to confirm the presence of HIV-1 infection.
Increasing Prevalence of Diverse HIV Subtypes
Further evidence of the growing impact of diverse HIV subtypes for monitoring AIDS patients in the United States was reported by the University of Maryland School of Medicine. The study showed the prevalence of non-subtype B strains in the Baltimore metro area is about two percent, based on tests of 2,200 HIV patients. However, in the Maryland portion of the Washington D.C. area, 13 percent of the positive samples sequenced were non-B. The majority of non-B subtypes (80.8 percent) were from recent immigrants from Africa, of which 62.5 percent were women.
ARUP Laboratories Study
Similar data presented in another CROI poster, authored by ARUP Laboratories in Salt Lake City, showed that the prevalence of non-B subtypes has increased steadily from 2004 through 2008 with incidences of non-B subtypes in 30 of 43 states. The most dramatic increases were seen for subtypes A and C. The authors conclude: “Due to the potential impact on patient management, it is important to recognize the growing genetic diversity of HIV-1 in the U.S.”
The CROI research adds to the growing body of evidence documenting the increasing spread of divergent HIV strains in the U.S. The New England Journal of Medicine recently reported: “The continuing spread of HIV is causing a world pandemic of unprecedented genetic and geographic complexity. Five HIV subtypes and two circulating recombinant forms have each established a global prevalence greater than 2.5%, a level that virtually ensures continued presence in the decades to come.”
About the Abbott RealTime HIV-1 Test
The Abbott RealTime HIV-1 assay is among the most sensitive viral load tests available today, with a broad dynamic range capable of quantitating HIV-1 in plasma down to as few as 40 RNA copies per milliliter (mL) and up to as many as 10 million copies per mL. Unlike other assays, the Abbott RealTime HIV-1 test targets the highly conserved pol integrase region of HIV-1 and has demonstrated the ability to detect diverse group M subtypes as well as group N and O isolates. More than 300 laboratories worldwide have adopted the m2000 RealTime system and HIV-1 assay. The system is currently used in 20 countries under CE Mark approval.
About Abbott’s Diagnostics Businesses
Abbott is a global leader in in vitro diagnostics and offers a broad range of innovative instrument systems and tests for hospitals, reference labs, molecular labs, blood banks, physician offices and clinics. With more than 65,000 institutional customers in more than 100 countries, Abbott’s diagnostic products offer customers automation, convenience, bedside testing, cost effectiveness and flexibility. Abbott has helped transform the practice of medical diagnosis from an art to a science through the company’s commitment to improving patient care and lowering costs. Abbott’s history is filled with examples of first-of-a-kind diagnostic products and significant technological and research advancements.
About Abbott
Abbott is a global, broad-based health care company devoted to the discovery, development, manufacture and marketing of pharmaceuticals and medical products, including nutritionals, devices and diagnostics. The company employs approximately 69,000 people and markets its products in more than 130 countries.
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