Image: A chart showing the costs associated with TB screening of healthcare workers (Image courtesy of McGill University Health Centre).
Routine screening for and treatment of latent tuberculosis (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. A new study has found that the current strategy of annual screening of is ineffectively expensive, suggesting that a switch to screening only high-risk healthcare workers is needed.
“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,’’ said study corresponding author Prof. Dr. Kevin Schwartzman, of McGill University Health Centre (MUHC; Montreal, Canada), Research Institute of MUHC, and McGill International TB Centre, “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 3 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 from Qiagen. 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,’’ said study first-author Guillaume Mullie, 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.’’ Dr. Schwartzman added, “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.”
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.
“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,” said Dr. Schwartzman.
The study, by Mullie GA et al, was published May 17, 2017, in the journal BMC Medicine.
McGill University Health Centre
Research Institute of MUHC
McGill International TB Centre