TB and rapid HIV tests: A match made in heaven?
Or a Pandora’s box some might like to nail shut?
Suddenly, rapid HIV testing is on the horizon. So is the prospect that soon everyone from public health TB clinic nurses to outreach workers will be able to administer a fingerstick test for HIV. Experts say that within the next two years, a new generation of inexpensive whole-blood tests for HIV will begin trickling into the U.S. market.
The U.S. Public Health Service has resolved to issue new recommendations urging that health care providers be allowed to administer rapid HIV tests and to give out positive results without making patients wait for a confirmatory follow-up test, says Bernard M. Branson, MD, MPH. A medical epidemiologist at the National Center for HIV, STD, and TB Prevention at the Centers for Disease Control and Prevention, Branson is chief architect of the new recommendations, which were to have appeared in the Feb. 27 issue of Morbidity and Mortality Weekly Report.
In effect, the new recommendations should entice many more rapid tests onto the American market. CDC research abroad shows that two rapid tests paired together correctly can give sensitivity and specificity ratings approaching, or equal to, 100%, say Branson and other CDC experts.
Knowing TB patients’ HIV status will have many repercussions regarding how providers go about diagnosing and treating TB disease and in how they treat instances of TB infection or close contacts, says Bruce Davidson, MD, head of the National Tuberculosis Controllers Association (NTCA) in Atlanta.
Davidson and others say the rapid tests may overcome widespread reluctance which appears to affect both health care providers and patients to venture into the arena of HIV testing. That reluctance probably accounts for why HIV status is known for only about 30% of TB cases in the United States, says Davidson.
"We don’t know for sure why the rest aren’t getting tested," he adds. "I’d like to think it’s because even though we’re asking, the patients are saying no."
From a patient standpoint, the new rapid HIV tests offer two advantages: Because practically anyone, including an outreach worker, can perform them, patients don’t have to travel to a clinic setting. Plus, because almost all the new tests use whole blood, not serum or plasma, patients don’t need to have their blood drawn.
"If we’re able to get rapid results in the field, that could be enormously helpful in terms of the impact on treatment," Davidson says. "I’m not one who believes that treatable conditions, even if they’re not curable, are best left unknown. I think the sooner we can find HIV in our patients, the better."
About 2% of patients in TB clinics could be expected to test positive for HIV. That estimate is based on data from the pool of people, many of whom are at high risk for HIV, who took HIV tests in 1996, the latest year for which figures are available.
Implications for TB treatment are substantial, says Davidson. Current CDC recommendations say adult contacts of TB cases who are HIV-positive including contacts who are skin-test positive, and very close contacts should get 12 months of isoniazid prophylactic treatment (IPT), not the conventional six months.
In most instances, health departments exert no more than "a tenuous hold," as Davidson puts it, over people getting IPT. But with coinfected patients, health departments which have the resources to do so usually clamp down much harder by, for example, providing directly observed preventive therapy for such patients, says Davidson.
Plus, cases of active TB can be much harder to detect among coinfected populations than among HIV-negative populations. Treatment for people with active TB who are HIV-infected or have AIDS may also need to be altered in various ways.
Even before the health service broke the news of its turnabout, TB control experts had been sniffing the wind for news on alternatives to conventional HIV testing.
Recently, Davidson polled NTCA members to learn who was using rapid or noninvasive tests. TB controllers in Washington, DC, replied that they’d been getting an enthusiastic response to Epitope’s Orasure test, a non-invasive assay that uses cheek fluid, called oral mucosal transudate. Since last June, "all cases, suspects, and contacts have been offered the choice of the Orasure test or the regular test," says Kurt Brandt, MD, TB controller in the nation’s capital.
Collecting the oral specimen takes just three to five minutes, says Brandt, and HIV clinic counselors who double as phlebotomists provide the pre-test counseling. Although the chest clinic where the tests are used "batches" the specimens, so results aren’t available for two weeks, Brandt says that "almost everybody comes back to get their test results; and if they don’t, we go after them."
Virtually everybody offered the choice of the Orasure test vs. the conventional test has opted for the oral test, says Brandt. And since the chest clinic began offering Orasure, the percentage of people choosing to be tested for HIV is up by 10% to 15%.
That seems to argue that not having to submit to the phlebotomist’s needle is a big plus for patients except for one problem. People chose Orasure even when they knew they were about to have their blood drawn anyway for a syphilis test, says Brandt. Maybe some Orasure test-takers simply wanted an easy way to confirm HIV test results they’d already been given, he conjectures.
Mixed feelings about offering HIV tests
At a TB controllers’ conference held in Atlanta last month, many in the audience reported mixed results in their efforts to get staff and patients to warm up to the notion of HIV testing, rapid or otherwise.
It’s tough to bring up HIV testing in the confines of a busy public health clinic, some said; others said TB clinic nurses and outreach workers tend to squirm at the thought of asking people about their sexual behavior.
In Colorado, for example, research has found that private providers and public health clinics don’t always offer HIV tests because they find it tough to switch gears from TB to HIV, says state TB controller Richard Hoffman, MD. "For the most part, I’d say that TB workers are not prepared to deal with the HIV part of the disease," says Hoffman. "There are all the emotions that go with [getting the test]. And you have to address all the other needs that go with [a reactive test] the referrals for medical care and all the other components that differ from TB care."
Hoffman also foresees difficulty ahead in the way rapid tests will affect contact investigations. Though they overlap in some respects, contact investigations for HIV and TB don’t necessarily cover the same ground; that means test-givers not only would need training in HIV counseling (both pre- and post-test varieties), but they’d also have to be cross-trained in how to investigate contacts of coinfected patients.
Lots of problems raised by new tests
So are rapid HIV tests a Pandora’s box some would prefer not to open?
"I think there will be a lot of problems created by these new tests that haven’t yet been resolved," Hoffman says. "And, yeah, there may be an immature part of us that wishes we didn’t have to deal with these problems. We’ve got a lot of things to think through."
Even so, Hoffman says he’s eager for the new technology. "We’ve got to take care of these people, and we need the best tools available to do that," he says. "It’s true these tests will create a lot of issues and that we’ve got a lot to think through here. But they’re coming; anyone can see that."
At present, the only rapid test licensed for sale in the United States is Murex’s Single Use Diagnostic Specimen, or SUDS, test. According to FDA regulations, positive results for a SUDS test can’t be given out until they’ve been confirmed. The intent behind the FDA prohibition on giving out positive results from rapid tests was to protect people from getting a provisional positive test that later might turn out to be false, says Branson.
But another consequence of the prohibition was to discourage makers of rapid tests from submitting their products for approval. "If you can’t give out rapid test results, and if they cost more than conventional tests you can batch, that pretty much dries up your market," Branson points out.
Yet in recent years, CDC researchers working in Honduras and Uganda found that pairing the right two rapid tests together can give results approaching, or even equalling, 100% sensitivity and specificity, eliminating the worry that someone might be given a false positive, says Branson.
The Catch-22, thanks to FDA regulations, was that there was only one rapid test on the market in the United States.
After some soul-searching, a working group looking at the issue decided to take the plunge. Only by pushing for the release of single-test results, they reasoned, could they enable U.S. clinicians to get their hands on the two or more rapid tests they needed.
"It’s like we all hit ourselves in the head at the same time and went, Wow! We should’ve had a V-8!’ We should have made these new recommendations a long time ago," says Branson.
Hoffman reports that a hospital lab in his state charges $200 for a SUDS test (which typically is used when health care workers suffer needlestick injuries or other accidents that may require post-exposure prophylaxis). Murex lists its SUDS test for $10, however. Other test-makers who now sell products abroad say they would market their products in the United States for between $7 and $15 each.
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