Current strategy of annual screening in North America is expensive and ineffective

By Julie Robert, MUHC

Tuberculosis (TB) is a recognized hazard for healthcare workers, but the annual screening strategy currently in place in Canada and the United States is costly with very limited health benefits and should be reconsidered, according to a new study led by a team from the Research Institute of the McGill University Health Centre (RI-MUHC). The findings, published in the journal BMC Medicine, suggest health agencies in North America should consider switching to a targeted strategy focusing on high-risk healthcare workers only.

“The process we’ve been through to generate and publish our results has been challenging at times but certainly very gratifying. It’s great to see that our work has made a contribution to the literature,’’ says Guillaume Mullie (right, fourth year McGill medical student). “The support of Dr. Schwartzman (left, Director of the Respiratory Division at the MUHC and a professor of medicine at McGill University) and his team has definitely played a huge role in helping me focus on achieving my research goals. I do hope that our findings will help inform policy-makers regarding ways to improve current screening practices for tuberculosis in our healthcare system.’’

“The *background rate of TB in North American communities is much lower today than it was 25 years ago when there were epidemics of TB in cities across the United States. As such, the risk of healthcare workers being exposed and infected at work is also much lower,’’ says the study’s corresponding author Dr. Kevin Schwartzman, Director of the Respiratory Division at the MUHC and a professor of medicine at McGill University. “Our results suggest the annual TB screening protocol should be changed to reflect more accurately the epidemiology of TB in North America and potentially in other high-income countries, such as those in Northern Europe.’’

The researchers used published data to simulate the experience of a cohort of 1,000 workers who received a baseline negative test after hiring— considering duties, tuberculosis exposure, testing and treatment. They compared the cost-effectiveness of three screening strategies: annual screening (for all workers with significant patient contact), targeted screening (regular screening of only the highest risk workers), and post-exposure screening (screening only after identified exposure). They considered two tests to diagnose TB infection: the tuberculin skin test (TST) and the newer QuantiFERON-TB-Gold In-Tube (QFT) test. The results of this study show that the QFT test was found to be more expensive to use than the TST test, with limited, or no, additional benefits.

“We projected costs, morbidity, quality-adjusted survival and mortality over 20 years after hiring. One of the most striking findings was that the current annual screening strategy costs over $1.7 million to prevent one additional case of active TB in a healthcare worker, when compared to a more targeted screening strategy, which in turn costs around $400,000 more per additional case when compared to the post-exposure screening protocol,’’ says the study’s first author Guillaume Mullie, a fourth year medical student at McGill University. “The costs of current practices are quite significant for the healthcare system, and reconsideration of this long-standing recommendation may be warranted.’’  “Additionally, the more you test healthcare workers without true exposure, the more likely it is that when you do find a positive test it will be a false positive because the tests are never perfect.  ” explains Dr. Schwartzman who is also a researcher at the McGill International TB Centre – a hub for scientists worldwide who work together to fight tuberculosis.

According to the researchers, healthcare workers should not be called back routinely every year for testing just because that is the protocol.  Instead, only workers at a particularly high-risk, for example respiratory therapists performing bronchoscopies, or microbiology laboratory workers, should continue to be tested regularly regardless of stated exposure.  Other workers should be evaluated only after exposure to a contagious patient.

Caused by the bacteria Mycobacterium tuberculosis, TB remains a leading cause of morbidity and mortality worldwide.  In its active phase, it is transmitted in droplets when a patient coughs or sneezes. After first contact with the microbe, the disease can develop rapidly or remain latent for several years before activating.  Routine screening and treatment of latent TB infection has traditionally been an important part of TB prevention in Canadian and US healthcare institutions, but recent data have called into question its cost effectiveness

“Resources currently allocated to routine TB testing for healthcare workers in North America could instead be used to increase access to prevention, treatment and testing infrastructure and support in communities that are at higher risk of developing TB disease such as homeless, foreign-born and indigenous people,” states Dr. Schwartzman.

*Incidence of tuberculosis disease (per 100,000 people) in 2015 was 4.6 TB cases per 100,000 in Canada and 3 TB cases per 100,000 in the United States.


Tuberculosis skin test (TST) is commonly used worldwide to see if someone has been exposed to tuberculosis. If you have ever been exposed to the TB bacteria, your skin will react to the antigens by developing a firm red bump within 2 days. The reaction is read by measuring the diameter of induration (palpable raised, hardened area) across the forearm.


Related coverage
Montreal Gazette

July 31, 2017