FDA Approves Novel Early Detection HIV Test

From Medscape Medical News

Yael Waknine

June 22, 2010 — The US Food and Drug Administration (FDA) has approved, under expedited review, the first assay to detect the HIV p24 antigen as well as antibodies to HIV types 1 and 2 (Architect HIV Ag/Ab Combo Assay; Abbott Diagnostics), potentially allowing patients to be diagnosed days earlier than with antibody-only tests.

The p24 HIV antigen is a protein produced by the virus immediately after infection, before the emergence of antibodies. Early detection is critical for controlling viral spread — the company revealed that every 9.5 minutes, someone in the United States is infected with HIV, and 1 in every 5 of these infected individuals does not know it.

"Since individuals are most infectious to others shortly after infection, detecting HIV earlier is critical and life saving," said Peter Leone, MD, medical director, North Carolina HIV/STD Prevention and Control Branch, University of North Carolina, Chapel Hill, in a company news release. "A significant percentage of new HIV infections are transmitted by someone with an undetected acute infection, so identifying more people earlier offers a significant opportunity for counseling, which can reduce high-risk behaviors and also initiate antiretroviral treatment for early-stage infection, if appropriate."

Most tests currently used in the United States detect HIV antibodies only. Although HIV infection can be directly detected via nucleic acid testing, this method is not widely used.

"The approval of this assay represents an advancement in our ability to better diagnose HIV infection in diagnostic settings where nucleic acid testing to detect the virus itself is not routinely used," said Karen Midthun, MD, acting director of FDA's Center for Biologics Evaluation and Research in an agency news release. "It provides for more sensitive detection of recent HIV infections compared with antibody tests alone."

In a behavioral intervention study conducted by Johns Hopkins University and Abbott, 217 blood samples were collected from men who have sex with men. Using 2 different HIV RNA tests as a control, researchers found that the combination antigen/antibody assay detected nearly two thirds (61.9%; 13/21) of acute infections, whereas only 14.3% (3/21) of acute infections were identified by third-generation antibody tests.

The chemiluminescent microparticle immunoassay is indicated as an aid in the diagnosis of HIV-1/HIV-2 infection in adults, including pregnant women, and children as young as 2 years of age. The new assay will run on the company's automated Architect ci8200 system and is expected to be available later this year.

The FDA notes that although the HIV antigen/antibody assay is not intended for routine screening of blood donors, it may be used in urgent situations when licensed blood donor screening tests are unavailable or impractical.

The combination test previously was approved for European use in 2004, with HIV antigen-antibody combination testing being routine in European public health settings and indicated for first-line use in the United Kingdom.