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It’s fair to say the TB standard proposed by the Occupational Safety and Health Admin istration (OSHA) has prompted a sustained series of gripes, indignant howls, and general grousing from the various camps that oppose it.
Foremost among OSHA-targeted gripes is that the most current data on skin-test conversions — still the best available gauge of how many health care workers are exposed to, and infected by, patients they encounter at the workplace — show emphatically that rates are way down.
"These data basically say that rates of transmission are now so low they can hardly be distinguished from background rates" in the surrounding community, says Edward Nardell, MD. Nardell is chief of pulmonary medicine at the Cambridge Hospital at the Harvard School of Medicine and TB controller for the Massachu setts Department of Health. As for the few workplace conversions that do occur, "there’s pretty convincing evidence that community transmission accounts for at least some of [that]," he adds.
Another gripe has to do with the way the OSHA standard would have hospitals and other institutions use respiratory isolation like a big, heavy-handed club when something more subtle would work a lot better.
"In many low-prevalence areas, we’re over-isolating patients at a ratio of as much as 200 to 1 to rule out TB," says Nardell. "In my own institution, the isolation rooms are almost always full; but in my hospital, and in most places, there are very, very few cases of actual TB." The practice of over-isolation siphons resources from other areas and, sooner or later, is bound to generate a backlash, he says.
The fact is, Nardell adds, some undiagnosed cases always will slip through; trying to operate at zero-risk levels is not only foolish, it’s unconscionably expensive. Far better to spend the money looking for "better ways to diagnose infection and disease," he explains. Tools already available include ultraviolet air disinfection and molecular probes (such as the Gen-Probe Amplified Mycobacterium Tuberculosis Direct Test, which can help to quickly rule out TB in patients in isolation).
Lower conversion rates will be considered
As might be expected, OSHA officials see things in a different light. For one thing, OSHA is well aware of the existence of data documenting lower conversion rates and is studying it, says Amanda Edens, MPH, OSHA’s project officer for the TB standard.
"We’re looking at new data right now, and it’s something we’ll certainly take into consideration. If it seems to be appropriate, we’ll make adjustments in what we’re proposing," Edens says.
Still, falling conversion rates don’t obviate the need for a federal guide. If anything, they demonstrate that the proposed standard, which hews closely to CDC guidelines, actually does what it’s supposed to, says Edens.
"What these new data show are that when you do the right thing, you can have a risk reduction," she adds. "That’s the whole point of having guidelines."
As for the difficulty of addressing the problem of "the undiagnosed case," Edens disputes that a new standard inevitably would fail in that regard.
"To my mind, there are two kinds of scenarios involving what people call the undiagnosed case,’" she says. "In one instance, you have a good identification system, you’re doing all the right things to identify cases that come in, and there may still be cases that slip through. And yes, that’s a real possibility."
In the second scenario, the undiagnosed case escapes notice because there are no systems in place; people are not "doing the right thing."
The problem is deciding whether most exposures and infections result from scenario No. 1 or 2, she says. Right now, OSHA statisticians are sifting instances of undiagnosed cases to see if they can spot the prevailing trend.