New rapid HIV tests fare well in study
New rapid HIV tests fare well in study
CDC researchers evaluate available tests
The good news is that there are at least a few rapid HIV tests that can accurately detect HIV seroconversion as soon or sooner than the standard enzyme immunoassay (EIA) test. However, these tests still need to be approved before clinics and prevention programs can reap the full benefit of their technology.
"None of these are approved yet, and the manufacturers have to do their own studies," says Bernard Branson, MD, chief of the HIV diagnostics and surveillance methods section of the Division of HIV Prevention at the Centers for Disease Control and Prevention in Atlanta. "The CDC feels it’s crucial for several reasons to get a rapid test on the market, and one big factor is because a lot of people don’t come back to get their HIV test results," Branson says. "And up to 30% of people who test HIV-positive don’t ever receive their results."
When rapid tests are available, a testing site could give a person the results within 10 to 20 minutes, making it possible to take a sample of blood and then give the person preventive counseling while waiting for the results, Branson notes.
All rapid tests outperformed SUDS
To this end, CDC investigators have studied the specificity and sensitivity of a variety of new rapid tests, including Determine, MedMira, Multispot, OraQuick, OraQuick oral, Quix, Hemastrip, and Unigold, compared with the only approved rapid test, SUDS, which was first available in 1992. In data presented at the retroviruses conference, the studies found that most of the rapid tests had very high rates of sensitivity and specificity when tested on stored serum, whole blood, and plasma, and all performed better than SUDS with stored serum and whole blood.1
Five of the rapid tests — Determine, Hemastrip, OraQuick, MultiSpot, and Unigold — identified an HIV positive sooner than did the Abbott and EIAs.2 "When we looked at the SUDS test, it showed somewhat more false positives than some of the newer rapid HIV tests," Branson says. Also, the SUDS test has a slower processing time than the newer tests because the serum or plasma tested by SUDS has to be spun and then tested.
"In one study where they did the SUDS test in an emergency room, they’d draw specimens, and there was an average of 150 minutes before the results came back to the patient," Branson says. "With OraQuick and Determine, you can use a finger-stick sample, so it’s a different process."
The SUDS test also takes longer to pick up on early HIV infection. For all of these reasons, rapid tests like OraQuick and Determine would be better choices to use in outreach HIV testing settings, Branson says.
The CDC currently is studying the OraQuick test under a special Food and Drug Administration (FDA) classification, called Treatment Investigational Device Exemption, at 12 sites in five cities. It’s being used to screen pregnant women in labor who come into the hospital and don’t know their HIV status, Branson says. "The study is the Mother-Infant Rapid Intervention at Delivery, and it’s just gotten started," Branson explains. "So far we have identified two women who came into labor with unknown HIV status and who turned out to be positive." Once they were identified as HIV-positive, it was possible for clinicians to treat them and their infants with antiretroviral medications in order to prevent their transmitting the virus to their babies.
Also, the CDC is continuing to study rapid HIV tests and is starting the process of assessing about 70 rapid tests that are used outside of the United States, Branson says.
Rapid tests well-suited for outreach settings
Once the most efficient and accurate rapid HIV tests are FDA-approved, then public health officials and HIV clinicians might be able to increase the number of HIV-positive people who receive their HIV test results, Branson says. "A lot of these rapid tests could be used in outreach settings where the return rates are very low, so overall I think it would have a big impact on people to know their status," Branson says. Furthermore, the people who are given a positive result from a rapid test are highly motivated to return for the results of a Western Blot test, which would still be used to confirm results, he adds. "It stands to reason when you give a person a preliminary positive test result that they have the motivation to come back."
References
1. Branson B, Uniyal A, Fridlund C, et al. Performance of newer rapid tests for HIV antibody with whole blood and plasma. Presented at the 9th Conference on Retroviruses and Opportunistic Infections. Seattle; Feb. 25-28, 2002. Poster 599-T.
2. Branson B, Meredith N, Mei J, Hannon H. How well do rapid HIV tests detect seroconverters? Presented at the 9th Conference on Retroviruses and Opportunistic Infections. Seattle; Feb. 25-28, 2002. Poster 361-M.
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