Congregate segregation simple but effective
With tuberculosis cases on the rise internationally, experts are looking more closely than ever at the principles and practice of TB infection-measures aimed at protecting health care workers in resource-poor settings. Refining those principles, and making sure they’re applied correctly, is especially important in the 22 countries with a high burden of multidrug-resistant TB (MDR-TB).
"With MDR-TB, the stakes are much higher," notes Edward Nardell, MD, chief of pulmonary medicine at the Cambridge Hospital and director of TB research for the Harvard-affiliated non-profit, Partners in Health. Unfortunately, experience shows that in resource-poor settings there’s frequently a gap between what ought to be done, and what really happens, Nardell adds.
For example, when investigators at a hospital in Lima, Peru, recently evaluated every admission for TB, they found plenty of trouble — including TB cases that were smear-positive, multidrug-resistant, or complicated by coinfection with HIV. That means that on a [typical] ward of this hospital, you might find a patient with undetected TB right next to a patient with undetected HIV," Nardell points out.
But even if the index of suspicion were cranked high enough to find more such cases, what would the Lima hospital do with them? Putting each suspect or confirmed case into respiratory isolation is not a luxury available to facilities in most resource-poor settings, Nardell points out. The next best thing is to practice "congregate separation," he continues. That means one ward for TB cases; another for HIV or coinfected cases (preferably with single rooms for each patient); and a third for suspect or confirmed cases of MDR-TB. That way, health care workers can be forewarned, and take steps to protect themselves, from opening a window to donning a particulate respirator.
Looking at ventilation in Russia
When the setting shifts to a chillier climate — Russia, for example — there are different challenges, says Peter Cegelski, MD, MPH, senior medical epidemiologist at the Centers for Disease Control and Prevention’s (CDC) Division for TB Elimination. There, opening the window may not be an option for most of the year. That means paying more attention to modifications to ventilation systems, he notes — for example, moving heated air into and directly back out of a room; or if air is to be recirculated, cleaning it with ultraviolet germicidal radiation or high-efficiency particulate filters. That’s the sort of refinement he and others at the CDC are adding to current guidelines that will be tailored to the needs of settings such as the former Soviet Union, he adds.
Where Nardell and Cegelski diverge is on the issue of what to do when the worst happens, and a health care worker appears to have been infected with MDR-TB. TB experts headed to Partners in Health’s DOTS-Plus project in Lima are told to consider getting a BCG vaccine, says Nardell, who adds he’s thinking of doing so as well.
"We say that knowing it’s controversial, and that you’ll lose the efficacy of the TB skin test," he adds. But meta-analysis of BCG’s efficacy indicate the vaccine gives some protection, which is certainly better than none, he points out; as for the loss of the TST, perhaps Quantiferon, the new diagnostic test which measures serum levels of gamma interferon, will prove its worth as a feasible substitute.
Cegelski disagrees. "I’d advocate against BCG’s use for someone going overseas to work in high-risk setting, since there’s no evidence it protects adults," he says.
Both men agree there are no data to say whether prophylactic regimens advised for those infected with MDR-TB — generally, a fluoroquinolone, plus pyrazinamide (PZA) or ethambutol — are worth the troublesome side effects they generally cause. "The experience with PZA and quinolones has been terrible," says Nardell. "People simply can’t take it for six months."
Maybe one of the newer and more potent fluoroquinolones could work solo, he concedes, but studies are lacking on that point as well. Cegelski says he’d probably take his chances and forego prophylaxis altogether, since the lifetime risk of developing TB from infection — even the often incurable variety of the multidrug-resistant kind — is, after all, only 10%.