“And if we can stop the transmission, we can stop the disease.”—Dr. Julio Montaner, director of B.C.’s Centre for Excellence in HIV/AIDS, July 19, 2012
At first glance, it seemed wasteful, almost insanely so. After the international AIDS conference in Washington, D.C., last week, health officials from B.C. were trumpeting mass population screening for HIV in their province, and eventually, beyond. According to the media reports, if we could get everyone who has ever been sexually active tested (on a volunteer, not mandatory, basis) it could mean “the beginning of the end” of AIDS.
Of course, there was much overselling in the media—with headlines like: “B.C. aims to end HIV/AIDS with widespread testing” and “B.C. launches massive program to wipe out HIV/AIDS.” But this screen-everybody approach also seemed dubious from a public health viewpoint. Given the well-known problems associated with over-testing, over-screening, and over-diagnosis in other areas of medicine—from PSA testing to pap smears—why try the catch-all method with HIV? What about the traumas related to false positives and the sheer monetary cost of such an encompassing plan? Plus, Canada doesn’t have a high prevalence of HIV/AIDS. Why would we adopt mass screening for a disease that mainly impacts marginalised or hard-to-reach groups that probably wouldn’t be captured anyway? Science-ish called Dr. Julio Montaner, one of the leading proponents of the program, to find out more.
Dr. Montaner, in his charming Argentinian drawl, began by working backwards to explain that the treatment of HIV (which causes acquired immunodeficiency syndrome or AIDS) is the most effective preventative tool we have. Once you identify a person with the virus, you can get her on antiretrovirals, which can extend her life and bring her viral load down so that she is less infectious.
“What we have seen is that HIV testing is the entry point into this whole cascade of care,” he explained. The trouble in B.C. was that public health officials had actually exhausted HIV testing in the at-risk communities. But it was difficult to capture the minority who may not have a known risk factor and may be living with the virus. With mass screening, he said, “We’re hitting the gold mine.”
Dr. Montaner’s idea of “the gold mine” comes from the results of a mass-screening pilot project that rolled out last October in the internal medicine departments of three Vancouver hospitals—St. Paul’s, Mount Saint Joseph and Vancouver General. Between 2,500 and 3,000 people were tested for HIV. Of those, about one per cent tested positive. According to Dr. Montaner, at least half of those people did not know they were at-risk and wouldn’t have been tested otherwise.
In a related review of people in Vancouver who tested positive in the last three years, researchers found that more than half of them could have been diagnosed during earlier visits to the doctor or the hospital, which suggests they were being tested (and treated) too late. By offering screening whenever people go see a health-care practitioner, the logic goes, you may identify those living with HIV sooner, get them on treatment sooner, and improve their personal health and that of those around them.
This idea, though, rests on a few assumptions. According to Dr. Theo Lorenc, research fellow at the London School of Hygiene and Tropical Medicine, there’s some promising evidence in modelling studies that mass, voluntary testing, along with early antiretroviral therapy, has been effective in Southern Africa, where the incidence of HIV and AIDS is believed to be the highest in the world. “But it’s much less clear that such approaches would be effective or cost-effective in a low-prevalence setting like Canada.” As well, there’s the question of whether transmission rates can be reduced with mass screening. Previous studies on specific populations, such as men who have sex with men, found that community-based programs involving rapid testing and counselling did not necessarily lead to upticks in the number of people getting tested, and did not detect previously undiagnosed infections at a notable rate.
Besides, what about people who are scared of testing—those who suspect they might be HIV-positive but don’t want to get tested so they can tell others they don’t know? “I’m not sure the evidence gives us any clear guidance as to how to overcome these barriers,” said Dr. Lorenc. According to Dr. Montaner, some 97 per cent of people in the Vancouver pilot accepted an HIV test when offered. What do we know about the motivations of that other 3 per cent who didn’t?
Still, it’s worth noting that B.C.’s plan had a very smart workaround. Patients in Vancouver were asked whether they’d like to take the test to confirm they were HIV negative. “Since 99 per cent of people are going to be, that’s the right way to ask the question,” Dr. Montaner explained. “What this allows us to do is to create a different approach and infrastructure to the problem.” If the question about the test is flipped on its head, and testing is offered on a routine basis, it may seem less threatening. As Dr. Montaner envisions it, “The campaign aims to normalize HIV testing so that ultimately your GP will offer you the test just as they offer PAP tests or PSA tests to eligible patients.”
Another assumption underlying the plan to reduce transmission rates by increasing testing is that people who are found to have HIV will actually undergo and continue treatment, especially when it’s not fully subsidized in some provinces as it is in B.C. “Antiretroviral treatment is a complex regimen, often with some side-effects, and maintaining adherence can be a problem at the best of times, even in symptomatic infections,” explained Dr. Lorenc. “When people are asymptomatic, this is going to be even more difficult. And when patients may not be accessing standard health services, may have chaotic lifestyles, this will become even more of an issue.”
The money question
There are also financial costs to consider. Is this the best way to allocate health dollars? To find out, Science-ish emailed Dr. Greg Zaric, who specializes in cost-effectiveness analysis at Western University. He noted that two articles published in the New England Journal of Medicine in 2005 both found that routine HIV screening south of the border would be cost effective in settings with an HIV prevalence as low as 0.1 per cent. “In B.C., Dr. Montaner has estimated that there are approximately 3,500 people who are HIV-infected but not aware of their status. The province has a total population of approximately 4.6 million, of whom approximately 3.5 million might be in the target age range for this screening program.” This corresponds to roughly 0.1 per cent. While it is “dangerous” to say that U.S. results are generalizable to Canada, “it is certainly plausible that the new program could turn out to be cost effective.” We just don’t know yet.
The B.C. program will be expanding to emergency and surgery departments at the three Vancouver hospitals, as well as to primary-care settings. The results of these efforts will be measured and published down the road, as researchers try to determine the optimal frequency and health-care setting for routine testing. Before we begin trumpeting mass screening as the way to end HIV/AIDS, let’s keep an eye on what this pilot does for B.C.
And, for the sake of context, let’s keep in mind that we’ve only ever been able to eradicate one virus: smallpox. That came as a result of mass immunization with vaccines. “Getting rid of a virus through screening, diagnosis, treatment, and prevention of transmission has never been done, and would be much more difficult,” said Dr. Greta Bauer, an epidemiologist at Western University.
In fact, the most important outcome of B.C.’s experiment might be its contribution to shedding the HIV stigma. As it stands, in Canada, we have what Dr. Bauer calls “the world’s most punitive laws regarding HIV criminalization.” Non-disclosure of status before sexual activity is criminalized, even if the virus is not transmitted. “It may be better, from a criminal and liability standpoint, to not know one’s HIV status,” she noted. That, indeed, seems like the greatest deterrent of all.
Science-ish is a joint project of Maclean’s, the Medical Post and the McMaster Health Forum. Julia Belluz is the associate editor at the Medical Post. Got a tip? Seen something that’s Science-ish? Message her at firstname.lastname@example.org or on Twitter @juliaoftoronto