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Sensitive test spots newest HIV infections

Standard HIV tests can't identify people very recently infected with the virus, but a more sensitive test can, new research shows.
/ Source: Reuters

Standard HIV tests can't identify people very recently infected with the virus, but a more sensitive test can, new research shows.

By testing for HIV's genetic material in addition to antibodies against the virus in more than 3,000 people, Dr. Sheldon R. Morris of the University of California, San Diego and his colleagues identified 15 HIV-infected patients who the standard test would have missed.

In the first few days after becoming infected with HIV a person has extremely high amounts of the virus in the blood, meaning he or she can transmit the virus to others much more readily, Morris and his team note in the Annals of Internal Medicine.

Blood banks screen donors for HIV with nucleic acid testing, or checking for the building blocks of the virus's genetic material; this approach can identify an HIV-positive person about 12 days before that person begins making antibodies against the virus.

Standard rapid tests now in use for HIV screening look for these antibodies. While these tests can produce results in a half-hour, they will miss very early infections.

In the new study, Morris and his team looked at whether the genetic material test could identify more newly infected individuals than the current standard rapid tests. They tested 3,151 people seeking HIV testing at sites in San Diego County using both the nucleic acid test and the rapid test.

Seventy-nine people had HIV infection, 15 of whom had tested positive with the nucleic acid test but were negative with the rapid test.

Morris and his colleagues also offered study participants the opportunity to check their results by voice mail or on the Web. Those who tested positive with the rapid test were told on-site, while those who tested negative were told that if the more sensitive test identified HIV infection — the test takes a few days to produce results — they would be contacted within two weeks. Study participants who did not hear from clinic staff by then could call a voicemail number or log on to a confidential Web site to get their results.

Sixty-nine percent of the study participants who tested negative accessed their results through voice mail or the Internet, with about two-thirds of these individuals opting for the Internet.

It cost about $160,000 to set up the program, including the voice mail and Internet notification system, Morris and his colleagues note, for a cost of about $10,000 for each additional HIV infection identified. While the researchers didn't do a rigorous analysis of costs and benefits, Morris said the spending is well in line, and likely below, many other interventions in wide use such as breast cancer screening.

There are several potential advantages to identifying HIV infections very early, according to Morris. "We believe early detection and if possible early treatment should reduce the number of new infections."

While it's not clear whether very early treatment is better in terms of preserving immune system function, Morris added, "there is a suggestion that earlier starts may reduce overall morbidity and mortality related to higher rates of heart disease and cancer in those living with HIV."

While most centers do not use nucleic acid HIV testing, Morris told Reuters Health, "it should be available (at no charge) in places like Seattle, San Francisco, Los Angeles, and New York."

State regulations currently control how people get their results after HIV testing, Morris noted. For people who undergo HIV testing frequently, and have already received counseling, he added, getting negative results automatically could make the process less onerous.

"You could see for some people that convenience factor would be a plus to them, especially the people who are used to the system," Morris said.

"There's not that much infrastructure that really needs to be built to allow that," he added. "Once you've got that working, it pays for itself, obviously." This is because, Morris explained, less staff time will be spent on follow-up tests and counseling.