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Rick Harp: Welcome to Episode 13 of Infectious Questions, a public health podcast from the National Collaborating Centre for Infectious Diseases. I’m Rick Harp.
This episode continues our look at tuberculosis with NCCID’s Shivoan Balakumar. Hello again, Shivoan.
Shivoan Balakumar: Hello Rick.
Harp: Now once again, Shivoan, we’re going to hear from someone you met at End TB 2017, a meeting of the North American region of the International Union Against Tuberculosis. Who is this episode’s featured expert?
Balakumar: Dr. Ryan Cooper is an infectious diseases specialist with Alberta Health Services. He presented at End TB 2017 on screening and treatment of LTBI, or latent TB infection, in Alberta’s foreign-born population. I asked Dr. Cooper to describe how TB post-landing surveillance works in Canada, and to respond to a question we received on the best approach to on-going follow-up.
Dr. Ryan Cooper: We should probably start just reminding people that not all migrants are screened post-landing. So all migrants undergo an immigration medical examination prior to their departure (or, prior to their immigration), and that immigration medical exam will include a chest radiograph, and questions as to whether that migrant has had previous tuberculosis in the past.
If the chest radiograph shows scarring compatible with old TB, or if the history identifies previous TB treatment, then those migrants are evaluated for active disease prior to departure, and treated for any active disease. The vast majority, however, do not have active disease and therefore are allowed to migrate to Canada with one condition—and, that is, that they report to their public health officials post-arrival. So they’ve been flagged by CIC [Citizenship and Immigration Canada: now Immigration, Refugees and Citizenship Canada or IRCC] and then referred to the public health program in their region that they land in.
Within that group that are referred, they all will have a chest x-ray that’s abnormal or a history of previous TB treatment. Our first task is to identify—when we see them, we repeat the chest radiograph and repeat a symptom inquiry because there is a proportion of those migrants who will have progressed to active TB over the period of time it took for them to leave their country and get settled and report to a public health officer. So we repeat the chest x-ray once they land and we repeat symptom inquiry, and occasionally we find active TB. And so, I think that’s actually really important. However, the vast majority of those migrants—and it’s about 2,000 a year to Alberta—won’t have active disease. So what do we do then?
The next step is to decide whether or not they’ve had inactive TB that might benefit from preventative therapy. For these individuals, we usually test them with a tuberculin skin test [TST], and if it’s positive they would be eligible for TB preventative therapy. This is an important intervention because this group that is referred by CIC, with a chest x-ray, scarring or a previous history of TB—they actually have a much higher risk of progressing to TB post-arrival than any other group of migrants. So if we can get preventative therapy into this group, that’s really beneficial.
And so a tuberculin skin test is a very sensitive way of screening, even in populations that have BCG vaccination. This group is high enough risk that if the tuberculin skin test is positive, I would offer them treatment.
QuantiFERON or other type of IGRA could be done; it would offer an advantage of being more specific, especially in this population with BCG vaccination. But of course there are costs associated with the QuantiFERON, but it does add that specificity so that you don’t over-treat migrants unnecessarily.
A lot of our migrants post-arrival have a history of previous TB treatment, and if it was a poorly-documented history of treatment, or the treatment was documented but was considered inadequate so they didn’t receive the standardized TB treatment regimen, those individuals would be eligible for preventative therapy post-landing as well. We don’t need to repeat a TST in this instance, we just offer them another course of preventative therapy, because if their treatment was inadequate they remain at some risk of relapse.
Of course, a lot of our migrants do have evidence that they received adequate therapy. Perhaps they migrated from a country and have the documentation that they received six months of standard TB therapy. This group, if it is reasonably well documented, we don’t offer them any further therapy. We consider a good six months of standard TB treatment to be adequate.
Nonetheless, for most countries in the world, drug resistance testing or culture facilities, they’re just not available. And so, we probably never know whether the patient actually received perfectly adequate therapy, so for almost all of these patients, if we don’t identify… if they’re not eligible for preventative therapy, we follow them for two years post-arrival with an x-ray every two years. And that is on the small chance that they might reactivate post-arrival. And we do see cases that way. We do capture them that way.
I guess, in summary, the purpose of that landing surveillance is to offer a latent TB treatment to those who are eligible (so, those who have never had a previous history of treatment), and to do chest x-ray surveillance for those with a previous history of TB treatment in case that treatment wasn’t precisely adequate.
Balakumar: Again, that’s Dr. Ryan Cooper of Alberta Health Services. I also asked Dr. Cooper to describe some of the Alberta-specific challenges that go with post-landing TB surveillance for newcomers.
Cooper: So our challenge is… we have a few here. One, it’s a large volume of patients. It’s about 2,000 people who are referred by CIC every year. We have about eight TB clinicians in the province, and so that’s a lot of chest x-rays to review, a lot of histories to review. That’s a program that has to be adequately resourced; you need to have people and time to interview these patients, and take chest x-rays, and guide their surveillance.
I think there are a few other challenges with this program, and I think that requires the need for expertise. One, we often find other non-TB-related conditions on this post-arrival surveillance, they can have airway colonization with non-tuberculosis mycobacterium, and so sometimes we end up having to address non-tuberculosis-related medical issues or investigate other types of infections that we accidentally find.
I think there’s also a challenge that undergoing this post-arrival surveillance, I think, can be stressful for the individuals involved. There’s always the fear that if we find something, that it’s going to adversely affect their immigration status, it’s going to adversely affect their ability to work, and their ability to remit money back to their family back home. And so there’s a lot of fear and stress associated with that, so we often spend quite a bit of time reassuring patients that no matter what we find, it does not impact their immigration status.
We emphasize that there is individual benefit for the migrant. I think that can’t be stressed enough. A lot of people sort of think of surveillance of TB, or screening for TB amongst migrants, is to prevent transmission to other Canadians, but we actually don’t see a lot of transmission to other Canadians from migrants. But I think a major purpose of this screening is for the health benefit of the migrant. It’s for their own… it’s to prevent them from getting TB and spreading it to their own family members. And so I think that needs to be emphasized to them that, if we did find TB, it does not impact their ability to migrate and that we can treat them, or we can prevent TB to an overall health benefit. We can safely do it.
I suppose though the biggest problem here is that the vast majority of TB in Alberta that occurs in the foreign-born does not occur in those under this surveillance process. Currently, LTBI screening, testing and treatment, is directed towards those with medical risk factors, or those with abnormal chest radiographs, or those with a close documented contact with tuberculosis. What this means is that patients who are otherwise healthy, with normal chest x-rays but born in TB-endemic country, are not eligible for TB screening under our current guidelines. But on the flipside, we find that most of our TB cases in the province actually occur amongst this group, occur amongst patients who are otherwise healthy, do not have classic medical risk factors like HIV or kidney disease. And it occurs amongst those who have normal chest radiographs.
So if we’re going to eliminate tuberculosis and we keep using our current strategy, we’re not going to get very far. We’re going to miss the vast majority of future cases of TB. So if we’re going to eliminate TB, we have to change our eligibility criteria for LTBI screening and we’re going to have to start screening people who are otherwise healthy. This might include migrants from highly re-endemic countries for TB, for example the Philippines or sub-Saharan Africa. And to do this group, to make it safe for them, might require more specific testing such as an interferon gamma release assay, like a QuantiFERON. That increased specificity will help us focus our treatment on those who are at the highest risk of reactivating, and those who most likely have latent TB infection.
The other thing we have to remember is that as their risk for TB goes down, the risk/benefit ratio of treating them before they reactivate starts to narrow. So, in other words, if you take a 35-year-old Filipino migrant without medical risk factors or an abnormal radiograph, their risk of lifetime TB is about five per cent if their TST or QuantiFERON is positive.
Now, their risk of an adverse event from TB preventative therapy is probably about one or two per cent, so you can see that the benefits of LTBI therapy outweigh the risk. But it’s a modest health benefit for that migrant.
Now, if we talk about an elderly migrant, someone who’s 65 years old who’s otherwise healthy and has no medical risk factors, now all of a sudden the risk of an adverse event from preventative therapy goes up. It’s getting close to five per cent, and their lifetime risk of TB remains at that five per cent. So now the risk/benefit ratio isn’t very close anymore. And I think that’s a danger: that if we start treating individuals—where their own personal benefit is too small to be valuable to them—because we think it offers a public health benefit, I think that’s risky and I would not recommend we do that.
So, we need safer regimens with less risk to the patient, and we need better tools to identify which healthy migrants will eventually progress to TB. Those tools might include better tests; I think the QuantiFERON is okay, but still not good enough.
Other factors might include, ‘Can we identify which of the otherwise healthy migrants are most likely to reactivate on the basis of their demographic features?’ So, does the incidence of TB in their country of origin impact things? We know that refugees are a particular high risk, so we should focus on them.
We know that migrants who migrate under a working visa for a healthcare class… so, if people like healthcare aides, nurses, nannies, they have a higher risk of getting TB post-arrival. Probably because, in their country of origin, they were healthcare people and associated… and exposed to TB more frequently.
So even amongst that large group of otherwise healthy migrants, if there’s a way that we could focus on those who are most likely to reactivate, that might make it safer for the individual patient and make those patients more likely to benefit from preventative therapy. And then of course that would have good benefits from a public health perspective as well. So that’s the tricky area, is how to safely provide preventative therapy at an individual level in order to make a public health impact.
Balakumar: My last question follows up on something Dr. Cooper said at End TB 2017—that is, a desire for Alberta to become TB-free by the time his daughter grows up. For that to happen, the province will need to address TB in other priority populations, namely rural, remote and indigenous communities. And according to Dr. Cooper, Alberta’s virtual TB clinic model has made a difference in this regard.
Cooper: Eliminating TB before my daughter grows up is an ambitious task for sure. But, you’re right, a component of that will require the ability to provide services to remotely-located patients, the ability to screen for latent TB infection in those at risk of TB who live outside of our urban centres who may live in reserve communities or Indigenous communities.
An additional challenge in Alberta is that our province bucks the trend a little bit in that not all of our migrants live in big cities. Many of them live in rural or small areas where the jobs are. We have a resource-based economy; many of the jobs that attract migrants are in small towns or in remotely-located communities, so that makes it difficult to get expert help.
Our program in Alberta has worked a long time at trying to address these needs because our province is big and people are spread out, and most of the medical expertise is concentrated in the cities. One way that we have addressed this problem is by setting up what we call a virtual clinic or a central TB clinic, and this is where physicians are based in Edmonton, review files from patients remotely located. And those files are collected by local public health nurses on the ground. So those public health nurses deal with everything in their community from vaccines to water-borne illness and also tuberculosis.
And so those nurses will assess clients, take a history, and obtain a tuberculin skin test and arrange for a chest x-ray, and sputum as necessary. That entire file is then sent electronically to Central TB Services, it is reviewed and then we dictate guidance to that local public health nurse as to how to best manage that patient.
We also have the ability to set up Telehealth interviews with patients as necessary, whether it be to consent them to a course of therapy or whether to gain better information that wasn’t acquired by the local public health nurse on the ground.
We have publications from our program suggesting that this virtual clinic is able to meet most performance metrics to the same degree as our urban centres, our Edmonton and Calgary TB clinics. So this virtual clinic does seem to provide effective care and safe care to the patients.
I do know personally that the ability to do Telehealth, I think, is looked upon favourably by the patients; they do enjoy that interaction with the physician. But for those that we can’t do that, they get to have close interaction with their local public health nurses. We know that the local public health nurses also love it because they get to interact with the patient in direct care, and know that they have an expert who’s sort of got their back and support them in that need. So we think it provides high-quality care, even to those who can’t travel all the way down to Edmonton.
Harp: Shivoan, thanks for bringing us your conversation with Dr. Ryan Cooper of Alberta Health Services.
Balakumar: You bet, Rick. And thanks to those who submitted questions to us through our NCCID newsletter.
Harp: And thank you for listening to Infectious Questions, a production of the National Collaborating Centre for Infectious Diseases.
Production of this podcast has been made possible through a financial contribution from the Public Health Agency of Canada. Note that the views expressed here do not necessarily represent those of the Agency.
The host organization of the NCCID is the University of Manitoba. Learn more at nccid.ca.