Wednesday, 23 November 2011

TUBERCULOSIS: In Canadian prisons

Tori Stafford/The Whig-Standard

The findings of a diagnostic investigation based out of Queen's University may help the fight against tuberculosis in prisons both nationally and around the world.
The Queen's-led program review looked at the diagnostic tools used by Correctional Services Canada when testing for Tuberculosis. Currently, tuberculosis skin tests are the standard tool used to screen for latent infections, both in prisons and hospitals in most of the country. The review compared the results of these tests to those of a newer diagnostic tool that involves blood testing, which Correctional Services is considering implementing.
The review was conducted by Dr. Wendy Wobeser, a professor in the department of medicine's division of infectious diseases with over 20 years experience in in tuberculosis research. Working with Wobeser were Paxton Bach, a student at Queen's school of medicine, and Ilan Schwartz, an internal medicine resident.
The team looked at 100 cases where inmates had tested positive for latent tuberculosis infection using TB skin tests.
"The current tool we use to screen for infection is the skin test, and it suffers from limitations in that it may be positive in people who have not truly been infected," Wobeser explained.
"For instance, in people who have had the vaccine for tuberculosis, the skin test may be positive, but they may not actually be infected."
Under the current Correctional Services policies, these inmates receive nine months of the medication isoniazid to prevent them from developing active TB in the future.
The team retested the inmates using the tuberculosis blood test Interferon Gamma Release Assays. Only 30% of the inmates tested positive with the new diagnostic tool.
"The new test ... was designed quite specifically to react in people who are infected and not be affected by previous vaccination," said Wobeser.
"So from a theoretical perspective, it represents a step forward."
From an effectiveness and efficiency standpoint, the findings indicate that, if in fact only 30 of the 100 cases are truly infected, only 30 inmates would need to undergo the preventative therapy TB program. Treating 30 inmates as opposed to 100 would drastically reduce the cost of this therapy.
"The Ontario region actually provides leadership for the country," Wobeser said, referring to correctional institution tuberculosis screening.
"But ... also for other jurisdictions in other parts of the world, because, really, they have in place a model screen program for tuberculosis."
Even though Correctional Service Canada sets the standard in tuberculosis screenings of prisons in other countries, improved screening could offer a number of benefits, including the cost reductions in treatments.
"Given that this is an airborne infection, the prisons are a very high-risk environment, so it's very important that a good screening program be in place," said Wobeser, who pointed out that a patient must have active tuberculosis, not a latent infection, to be contagious.
"I believe for the Canadian system this is quite a significant advance forward," Wobeser said.
"Not only would it make the program more efficient, meaning less people are on treatment, it actually makes it safer."
Although problems with the medications used to treat the infection are rare, Wobeser said, they do occur. Some patients experience liver inflammation from the medication.
"So by better targeting the treatment, we're exposing fewer people to the potential risk of the treatment," she said.
While most Canadians have received the TB vaccination, tuberculosis cases are still an issue in the country. Last year alone there were 1,600 reported cases of tuberculosis in Canada, Bach explained.
For Bach, a third-year medical student who moved to Kingston from Vancouver in 2009, being part of the investigation was an experience like no other he's had thus far.
"This has been a fairly unique project. I've done a lot of research in the past," said Bach, who's already obtained his masters in experimental medicine from the University of British Columbia.
"Both in the nature of specifically what we were doing, as well as the way that we were working with the government was pretty unique for me," he said.
Similarly, Schwartz found his experience with this project to be both "unique and interesting," specifically with regard to collaborating with Correctional Service and working inside maximum security Millhaven Institution.
"Many research projects involve reviewing charts or collecting data at hospitals, so it was particularly interesting to be liaising with and visiting a federal prison to accumulate this information."
Although the team's findings shed light on the discordance between the two tuberculosis screening methods, blood testing hasn't been around long enough to know if it's results are truly more accurate than those of TB skin testing.
"A number of jurisdictions have stopped using the skin test and they only do the blood test. In this jurisdiction, we're still doing both," Wobeser explained.
"There are a number of characteristics of the blood test that favour moving toward it, but this is an area of evolution... there's still things we need to learn about the blood test."
The teams finding that 70% of those who tested positive on skin tests, but negative on blood tests is in keeping with the findings of other areas currently testing the blood test screening, such as Alberta and San Fransico.
Wobeser, Bach and Schwartz recently presented the findings of their program review at the 42nd Union World Conference on Lung Health in Lille, France. The response to their display on their investigation was received with both interest and intrigue, the team said.
"People were quite interested in it, because it's a very topical question these days," Bach said.
"We're still using the skin test most places in the world to detect tuberculosis infection. Despite the fact that it's been around for over 100 years, we haven't come up with anything better."

No comments:

Post a Comment