Oral HIV test makers eye home-use market
For now, tests will stay put in the clinic
A new, rapid-assay home test for HIV called OraScreen uses oral fluids collected on a swab, costs less than a home-use HIV blood test, takes about 15 minutes, can be read on the spot, and is available over the counter — but only if you’re willing to hop a plane to Aruba.
A spokesman for OraScreen’s manufacturer, Foster City, CA-based Beacon Diagnostics, says the company isn’t optimistic about getting permission to sell the test to home users in the United States anytime soon because users don’t have to call a counselor to get test results.
In addition, questions about the new test’s sensitivity still need to be answered, says Bernard Branson, MD, a medical epidemiologist in the Division of HIV/AIDS Prevention at the CDC in Atlanta. "Until we have more information, I think we need to withhold judgment," he adds.
Still, makers of the newcomer product say they believe they’ll be selling OraScreen in the clinical setting in the United States within the next two years. In that event, OraScreen would try to position itself alongside OraSure, another test for HIV that also uses oral fluids instead of blood, and which was approved by the Food and Drug Administration last fall for use only in clinical settings. OraScreen currently is being sold only in the Caribbean.
The big difference between the two tests is this: the newcomer product, OraScreen, is designed to be read on the spot, while OraSure users must wait for results to come back from the lab.
Though neither test has been approved for home use, the makers of both products are clearly drooling at the prospect of eventually gaining access to the burgeoning U.S. home-test market.
SmithKline applies to FDA for home use
Although media contact representative Lori Agin says SmithKline "isn’t interested" in selling OraSure over the counter, the company has in fact applied to the FDA for permission to market the product for home use, says the CDC’s Branson. A second SmithKline spokesman (who asked not to be identified) says if OraSure were approved for home use, its users still would have to mail in their specimens and call later for results.
Thus, if both tests were approved for home use, the difference would again boil down to whether users would have to wait for results from the lab, or whether they could read them right away, as with a home-test pregnancy kit.
Perhaps with this difference in mind, spokesmen at Beacon Diagnostics are far less circumspect when it comes to talking about their long-range ambitions for OraScreen.
"I’m firmly convinced there are a large number of people capable of doing a test like this at home, and capable of dealing with the answers at home," says Bert C. Del Villano, PhD, Beacon’s executive vice president. "Frankly, I’d like to see someone with the resources get out there and organize the groundswell of demand which already exists for such a test."
Taking out the counselor will be a big step’
The stumbling block, as far as Del Villano is concerned, is the FDA’s reluctance to hand consumers a rapid-assay test that gives them quick answers, but doesn’t require any contact with a counselor, he says. Getting over that reluctance is probably going to take time, he adds.
"Confide was a big step," he says, referring to one of the home-collection, mail-away blood tests for HIV that hit the market last fall. "Taking out the counselor altogether would be another big step." (See related article on home blood-test kits, p. 21.) OraScreen includes a package insert that provides basic information in question-and-answer form about HIV and AIDS, its makers say. His company also is "urging" distributors in markets where the test is sold over the counter to provide free phone counseling, Del Villano adds.
It isn’t altogether clear how much benefit counseling actually provides to people who get an HIV-positive test, says the CDC’s Branson. "We don’t yet have good evidence of its impact in any setting," he says. "In a testing site where counseling’ is a short visit with a complete stranger, the benefit may not be that great."
The OraScreen test takes 15 minutes to perform from start to finish. In countries where it will be sold for home use, it probably will retail for a bit more than home pregnancy tests, but less than the home-use, mail-away blood tests already in use, says Del Villano. Available data show the specificity and sensitivity of the test are better than 99%, and that test accuracy is "virtually identical" to blood tests for HIV, he adds.
As for OraSure, the test that’s already approved, sample testing of 3,570 subjects in the United States "gave the correct result or triggered appropriate follow-up testing in 99.97% of cases," the company’s product literature says.
Until recently, attempts to use saliva instead of blood to test for HIV ran into the same problem: for better or for worse, there is virtually no HIV virus present in human saliva. Antibodies to the virus are present in saliva, but in concentrations so low (about 1/20,000th of the level in serum) they’ve been impossible to measure, says Jerome A. Mattingly, PhD, Beacon’s president.
To solve the antibody concentration problem, OraSure — and now, its makers say, OraScreen as well — have come up with essentially the same solution. Instead of saliva, each test aims to collect an oral fluid called transudate from capillaries that underlie the oral mucosa. In oral mucosal transudate (OMT), antibodies are present in concentrations that can be reliably and accurately detected by means of an enzyme-linked immunosorbent assay (ELISA), the tests’ makers say.
Though both products go after OMT instead of saliva, and both use an ELISA to screen the specimen for HIV antibodies, there are several differences in how the two tests are assembled and used.
OraScreen lacks confirmatory test
For one thing, the OraScreen test, being a home assay, doesn’t provide users a way to confirm positive results. With OraSure, by comparison, all positive results from an ELISA are verified with a Western Blot scale, a confirmatory test used to make sure the antibodies found by an ELISA are indeed specific to the HIV virus, and not to some other agent.
In practice, the lack of a back-up test means OraScreen users could get a false positive result, but not know it unless they sought confirmation from an outside source — a step the OraScreen test kit recommends for everyone who gets a positive result.
A bigger difference has to do with how and where in the mouth users collect the specimens.
With OraSure, which is only approved for use in the clinical setting, a health-care professional hands the patient a swab stick, instructs the patient to place the swab between the lower cheek and gum, and then times the collection of oral fluid, a procedure that is supposed to take exactly two minutes.
With OraScreen, home users put a pad under their tongues (not between their cheek and gum), and hold it there until a "window" in the stick turns blue, a signal that exactly one milliliter of fluid has been collected.
The under-the-tongue approach, compared to the gum-and-cheek method, works well enough to collect "reasonable amounts of transudate," adds Del Villano; but the CDC’s Branson says he isn’t so sure.
The underside of the tongue is a rich site not only for capillaries, but for saliva as well, Branson says. Thus, it’s possible the OraScreen swab might be collecting more saliva than transudate, he adds. "It’s my understanding that [the manufacturers] are having trouble verifying whether the test offers enough sensitivity," Branson says.
New test has three built-in controls
Less doubt exists about whether OraScreen’s makers have done a good job of making their product friendly for home users, and, at least from a user standpoint, as goof-proof as possible.
The dipstick collection method OraScreen has devised is evidently a reliable way to collect the single milliliter of oral fluid the test kit requires, Branson says. Also, the test’s makers have incorporated several built-in controls to make sure the kit’s reagents are working properly, and to make sure the buyer is using the kit correctly. (The controls consist of dipstick windows that either change color, or show a plus or minus sign.)
Issues of sensitivity aside, the biggest difference between the two tests is the way the OraScreen kit has, in effect, provided users with a miniaturized version of an ELISA, a step that lets them avoid the wait for results from the laboratory.
All the necessary components are contained in a series of small wells, starting with a substance that prevents the antibodies (if any are present) from deteriorating. The wells are numbered 1 through 7; into them, the user immerses a dipstick (which contains the oral fluid specimen) for a specified length of time.
As with a conventional ELISA, the result is a kind of "sandwich," made up of antigen (in the form of denatured HIV, already provided on the test-kit dipstick); antibody specific to HIV (from the user’s oral fluid, if any is present); and antihuman IgG that has been linked to an enzyme. A colorless substrate added to this three-part sandwich shows whether any enzyme is present by changing color.
Instead of the soluble end-product yielded by a conventional ELISA (which requires an unwieldy piece of equipment called a spectrophotometer to read), the entire process yields an insoluble, colored molecule that deposits itself on the dipstick. The user reads this as a clearly visible color change, in much the same way as in a home pregnancy test.
So when, exactly, will OraScreen hit the drugstore shelves? "My crystal ball doesn’t have that information," says Del Villano. "But sooner or later, we’ll be there."
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