In San Diego County, a program that integrated nucleic acid testing (NAT) with rapid-result HIV antibody screening helped increase the HIV case detection yield - especially in settings that cater to high-risk individuals, a new study shows.

Of 3,151 people screened, 79 were newly diagnosed with HIV. Sixty-four were diagnosed via rapid HIV test; however, 15 additional infections were found only by NAT. Thus, NAT increased the HIV detection yield by 23 percent.

"If people got an antibody test alone and were told they weren't infected when they were, they could be a strong infection risk until they get tested again, which according to guidelines could be six to 12 months later," said study leader Dr. Sheldon Morris, of the University of California-San Diego's Antiviral Research Center.

The NAT samples were sent to labs in San Diego and Emeryville in the Bay Area. Study participants could receive their NAT results in person with clinic staff or through an automated system accessible by telephone or website. About 65 percent chose an automated option. All NAT-positive patients received their results within a week.

It can take months before a newly infected person's body produces enough antibodies to register as HIV-positive on antibody test. The NAT can detect HIV within 10 days of infection, Morris said.

"I think the time is coming where we will have to adopt a strategy for earlier [HIV] detection," said Morris. "If you have a testing site with a high-risk prevalence, then you probably should be running this test on all of their samples" that are antibody-negative, he said.

For more information about the center's Early Test Program, visit http://avrctrials.org/. The study, "Evaluation of an HIV Nucleic Acid Testing Program with Automated Internet and Voicemail Syst