By Gary Evans, Medical Writer

The CDC is expected to issue new tuberculosis testing guidelines for healthcare workers that end routine annual TB screening in favor of a baseline test on hire and retesting after an occupational exposure, the co-author of the document tells Hospital Employee Health.

These revisions come as TB testing and treatment have improved, while the routine risk of healthcare workers acquiring TB at work has steadily declined.

“There is no literature to support” that healthcare workers are at high occupational risk of contracting TB from their patients anymore, says co-author Wendy Thanassi, MD, MA, MRO, a professor at Stanford University and chief of Occupational Health Services at the VA Palo Alto Health Care System in California.

Other factors in the decline of TB as an occupational threat are the engineering controls and prevention measures that have become routine in many hospitals.

“Hospitals have done such a good job with environmental controls — negative pressure rooms, air filters, air circulation, and identifying patients and wearing masks early,” she says. “We have seen transmission decline because of these environmental controls.”

The CDC reported 9,093 new cases of TB in the United States in 2017.1 That translates to a rate of 2.8 cases per 100,000 people, a decline of 2% from 2016 that continues a trend of TB reduction. For example, in 2000, there were 16,308 new cases of TB, a rate of 5.8 per 100,000 people. However, TB is still a threat, and employee health professionals should remain vigilant.

“People do have TB, which is a very serious disease,” Thanassi says. “Active TB has a 10% mortality rate. But it is very rare that we find it incidentally in a healthcare worker without finding it first in a source [patient].”

According to the CDC, the rate of TB “among non-U.S.-born persons in 2017 was 15 times the rate among U.S.-born persons. Previous studies have shown that the majority of TB cases in the United States are attributed to reactivation of latent TB infection.”

Some healthcare workers from countries with higher TB prevalence may have been administered the Bacillus Calmette–Guérin (BCG) TB vaccine, which is not routinely used in the U.S. Those vaccinated may experience a cross-reaction to a TB skin test, registering a false positive. The CDC currently recommends use of the TB blood tests for workers who have been immunized with BCG.

The new guidelines are expected to encourage broader use of the TB blood tests over the traditional skin tests, which often are performed in a more labor-intensive two-step approach to ensure accuracy. However, the new guidelines likely will state that those using traditional skin tests can continue to do so, as the CDC typically defers to local preferences rather than a one-size-fits-all approach in its recommendations.

Having used the TB blood tests exclusively for years, Thanassi says the focus should be using the blood tests on hire and treating latent TB at that point rather than conducting routine screening thereafter. There also are new effective treatments of shorter duration for healthcare workers with latent TB, which can remain dormant for years before activating.

“When we find people who are positive based on these blood tests, we can have them treated for their latent TB right away,” Thanassi says. “This obviates the need to test people every year because we are not finding that healthcare workers are converting year to year. The next testing that would be necessary for employees would be upon exposure to an active TB case.”

Such routine testing of healthcare workers is yielding a succession of negative tests in the 97% range and is no longer a good use of employee health resources, she adds.

“This removes a lot of unnecessary time and money expended,” Thanassi says. “Hopefully, it will allow occupational health to stop spending time with negative tests and redirect their focus to the employees who do have latent TB, and start treating them. I believe it is a public health imperative to identify and treat these employees right away.”

As of press time, the CDC had not issued the new guidelines. While Thanassi expected they would be released soon, a CDC spokesman was less definitive.

“We are reviewing the current guidelines and may update them later this year,” says Scott Bryan of the CDC National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention.

Another co-author of the guidelines, Lynn Sosa, MD, a TB epidemiologist at the Connecticut Health Department, declined a request for comment until the CDC update is published.

In anticipation of the new guidelines, the Association of Occupational Health Professionals in Healthcare (AOHP) slated a session on the topic this year at its annual meeting, Sept. 4-7 in Baltimore.

“Currently, many occupational health professionals are obligated by local or national policy to conduct up to tens of thousands of TB tests annually,” according to a statement from AOHP.

“The updated national guidance will empower practitioners, in most cases, to eliminate annual TB testing while maintaining pre-placement and post-exposure testing, as well as to advocate for treatment of those with latent TB infection.”

As of press time, the current CDC guidelines2 say facilities can use the TB skin test or blood test for healthcare workers at baseline, and then retest thereafter depending on risk categories.

Risk factors include the prevalence of TB in the patient population and the community. Hospitals at medium risk are recommended to test healthcare workers annually.

The new CDC guidelines are expected to drop the risk categories, essentially conflating them down to the low-risk recommendation of retesting healthcare workers only if there has been a TB exposure incident, Thanassi says.

Ending HCW Angst

HEH asked Thanassi to comment more on the TB testing program at the VA Palo Alto Health Care System in the following interview, which has been edited for length and clarity.

HEH: How have you approached TB testing of healthcare workers?

Thanassi: We have not used the skin test since January 2009. For 10 years, we have recognized the value of the blood test over the skin test, which has a lot false positivity related to people who were born in another country and had the BCG vaccine, or who came in contact with non-TB mycobacteria.

We recognize the importance of the blood test in getting an accurate diagnosis. We were one of the first major centers to switch entirely to using the blood tests. We have a history of tens of thousands of tests now. None of the generations of the blood test cross-react with the BCG. That has been an advantage of these from the very beginning.

HEH: Why is that such an important factor?

Thanassi: It is very important because there are many employees walking around in fear that they have TB because they have been told that their skin test was positive. They worry that they may be taking a year of toxic medications, maybe they should be worried about [exposing] their newborn baby or their elderly grandmother.

So, if we can take those people who had a positive skin test — who believe for maybe a decade that they have latent TB — and offer them the blood test, we can tell them quite definitely that they do not have TB, that it was a cross-reaction with their old vaccine.

HEH: That is an aspect of TB testing that is not often emphasized.

Thanassi: It is a tremendous weight off their chests. It is quite important to take that burden from people.

There are a lot of benefits to the blood tests on a personal level that sometimes may go unrecognized. We will have a lot of wonderful healthcare workers in the U.S. who come to us from the Philippines, Mexico, Vietnam, India. They are tremendously well-trained healthcare workers; they just came from an environment where they got this vaccine because their country has a higher prevalence of TB than we do.

HEH: How have TB treatments improved?

Thanassi: TB treatments have changed dramatically in the last decade. The treatment for latent TB used to be nine months of daily isonicotinylhydrazide (INH), which is quite liver-toxic. This toxicity can put people in the hospital and occasionally causes fatalities. It had about a 67% efficacy rate because there was a lot of noncompliance with that long of a treatment program.

Now we have a treatment that is just three months, once a week of INH plus rifapentine. Essentially, it is 12 weeks of antibiotics to get rid of latent TB. The combination of these new tests that are accurate and a new treatment that is short and safe means that we really should be able to take care of latent TB before it reactivates.

REFERENCES

  1. Stewart RJ, Tsang CA, Pratt RH, et al. Tuberculosis — United States, 2017. MMWR 2018;67:317–323.
  2. CDC. Testing Health Care Workers. Available at: https://bit.ly/2VvLa5J.