The Bay Area Reporter - September 25, 1999
Liz Highleyman

The strategy, dubbed Serologic Testing Algorithm for Recent HIV Seroconversions, or STAHRS, uses a recently developed antibody test called the detuned ELISA. The modified assay was developed at San Francisco's Blood Centers of the Pacific (formerly Irwin Memorial Blood Bank) in collaboration with the CDC. The standard ELISA test can typically detect HIV antibodies in the blood after three to four weeks. The detuned ELISA, a less sensitive version of the test, cannot measure low levels of antibodies, and can only detect infection after about 120 days. Thus a person who tests HIV-positive using the standard ELISA, but HIV-negative using the detuned ELISA, was most likely infected within the past four months.

Prior to the development of the new test, researchers could only determine the total number of infections among people who were tested, which epidemiologists refer to as prevalence. The detuned ELISA provides information about the number of new infections, or incidence. In a mature epidemic û especially one with a long incubation period between infection and eventual illness û prevalence data is less useful than incidence data in predicting where and among whom new infections are occurring.

At the Atlanta conference, researchers reported the results of a study of 96,000 clients of sexually transmitted disease (STD) clinics in six U.S. cities. The results indicated that 8 percent of gay and bisexual men are infected with HIV per year, compared to .48 percent of heterosexual clients at the same clinics. According to CDC researcher Dr. Robert Janssen, "It's the first time we have had timely HIV incidence data on a broad scale. à We can now better identify new epidemics while they are still just emerging, and intervene before infection spreads more broadly."

In 1997, the San Francisco Department of Public Health (DPH) requested that the city's HIV Prevention Planning Council allocate funding for a pilot study that would use the detuned ELISA to retrospectively test stored blood samples that had been collected in HIV serosurveys conducted between 1989 and 1996. At that time, the DPH's Sandy Schwarcz said that, "The ability to identify newly infected persons now opens the door to a wide range of previously unavailable prevention opportunities," and suggested that the detuned ELISA could help identify which populations are most at risk and which behaviors contribute most to new infections.

In September 1998, the city's HIV test sites began using the detuned ELISA; to date, several thousand individuals in the Bay Area have received the new test. According to Dr. Willi McFarland of the DPH, 20 percent of those who tested HIV-positive were in the first four months of infection. The "vast majority" of recently acquired HIV infections were seen in white gay or bisexual men in their 30s, especially gay and bi men who inject drugs. One new infection was detected in a heterosexual woman; none were seen in non-gay injection drug users.

At the Sixth Conference on Retroviruses and Opportunistic Infections this past February, Dr. Michael Busch and colleagues from the Blood Centers of the Pacific reported the early results of a study that used the detuned ELISA to screen 5.2 million blood donors (including 1.8 million first-time donors) across the U.S. That study revealed that the rate of new HIV infections was greatest in the Southeast U.S. and among the poor and ethnic minorities. According to Busch, with the new test, "We can now, for the first time, measure the incidence of infection in a large population." McFarland said that the apparent discrepancy between the national and San Francisco results is not surprising, given that "San Francisco has a very different epidemic."

The detuned ELISA has elicited some controversy among those who fear it may be used to facilitate tracking of HIV infections. Public health officials hope that individuals will be more successful at remembering their sexual partners over a short, four-month interval. Contact tracing and partner notification are standard practice for STDs such as gonorrhea and syphilis, but are not used for HIV in California due to concerns about privacy and discouraging voluntary testing. Currently in California, only AIDS cases, not HIV infections, must be reported by name; the CDC has pressured states to begin reporting HIV infections as well, and many states already do so. A bill authored by Assemblywoman Carole Migden (D-San Francisco) and recently passed by the California Legislature would implement a system of HIV reporting based on anonymous unique identifiers. The bill is awaiting approval by Governor Gray Davis.

Some are concerned that the availability of the detuned ELISA will encourage public health officials to institute mandatory contact tracing and partner notification, especially for the low-income and disenfranchised populations that are more likely to use public clinics. According to Michael Petrelis of the AIDS Accountability Project, "I want hard, independently verified figures on everything associated with this test. Until more honest numbers and science are produced, I don't trust those who advocate its development."
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