Experts take aim at TST at recent IOM hearings

But, chair adds, OSHA will have its day, too

No one could blame supporters of the federal TB standard proposed by the Occupational Safety and Health Administration (OSHA) if they ran home from a recent hearing by an Institute of Medicine (IOM) committee and grabbed a headache powder and a cold compress.

Held in August, the two-day stint of testimony and discussion was the second meeting for the IOM committee that Congress charged late last year with determining whether TB poses a sufficient risk to health care workers to justify creating a federal standard.

At the end of the second day, session chair Walter Hierholzer, MD, professor emeritus of internal medicine at Yale University in New Haven, CT, seemed to acknowledge that the weight of the hearing’s evidence was tilting strongly against OSHA. But, he added, "there will be other days" when that won’t be the case.

First, OSHA partisans in the audience listened as the opposition dissected the agency’s estimates of annual mortality from TB.

When it was time to work over OSHA’s estimates of morbidity, which are based on data from skin-testing programs, OSHA opponents traded their scalpels for sledge hammers, as various experts testified to the unreliability of the tuberculin skin test (TST).

Union representatives and experts from occupational medicine, two camps that have spent years advocating on behalf of the OSHA standard, also were on hand. They presented evidence, much of it anecdotal, intended to show that some unscrupulous employers are not abiding by federal guidelines. Only the force of law, they added, will force such facilities to toe the line.

"I actually came away from these hearings with a better appreciation of their point of view. It’s true that there are some bad actors out there," notes Ed Nardell, MD, chief of pulmonary medicine at the Cambridge Hospital of Harvard Medical School and medical adviser to the TB control program for Massachusetts.

The problem is that OSHA, which must show substantial risk to workers before it can propose and implement federal regulations, has based many of its measurements of risk on TST data. As one expert after another at the IOM hearings argued, the skin test isn’t a good indicator of true conversion rates in low-prevalence settings.

"So what do you do?" Nardell asks. "You can’t just ignore the science altogether."

In a press conference held after the second day of testimony wrapped up, even OSHA chief Charles Jeffress seemed to hedge a bit in his resolve to press forward with the TB standard. Mostly because the ergonomics rule is uppermost in everyone’s mind at OSHA, Jeffress conceded that the TB standard probably will miss its latest deadline, set for the year’s end.

In the OSHA offices in Washington, DC, Mandy Edens, MPH, chief project officer for the TB rule-making process, said she was planning to set work aside for the next two months and devote herself to other tasks.

And, Jeffress added, if IOM committee findings, which are due out by December, go against OSHA, that might — just might — have an effect on what the federal agency does next. "Whatever information comes out of the IOM study, depending on where we are in the process, it might affect what we do," was the way the OSHA chief put it.

The benzene decision sets precedent

To understand the twists in the latest bout of wrangling between pro- and anti-OSHA forces, it helps to go back to the rationale for devising a TB standard — or any standard, for that matter — in the first place.

In 1980, when OSHA was trying to come up with a way to protect workers against the carcinogenic effects of benzene, the petroleum industry sued the agency, accusing it of being too vague in its charges that benzene created a "significant risk" to workers’ health. The Supreme Court agreed: OSHA needed to quantify the risk and needed to come up with a risk great enough that a "reasonable person" would act to protect himself, the court said.

With TB, OSHA has tried to quantify two endpoints, says Edens: deaths and the risk of becoming infected. "Obviously, there’s a greater risk for [skin-test] conversion than for death, so the focus of our risk assessment has been to get data to quantify the risk to health care workers [for conversion," she adds. "We acknowledge that the available data aren’t always the best, but they’re what’s available, and you have to deal with the data you’ve got."

OSHA argues that skin-test conversion, insofar as it signifies TB infection, does constitute what the agency terms "an adverse event."

"Some people argue the skin test is beset with false positives," Edens concedes, "and it’s been argued that being infected doesn’t impair your everyday life, at least not in the way that losing an arm or a leg does."

Defining adverse’

But for some people, becoming TB-infected is an adverse event, she adds. "For one thing, prophylactic therapy carries with it some risks," she says. "For those who can’t take isoniazid, there’s the risk of developing disease. Plus, there’s the emotional concern engendered among people who convert."

Latent infection is construed as an "adverse event" in OSHA’s bloodborne pathogens standard, which seeks to protect workers against the risk of contracting hepatitis B virus. "In that case, the main focus of our assessment was not getting the disease itself but becoming infected," she notes.

All this helps explain the weight of arguments — some based on traditional arguments, some on newer data — about the frequency of false-positive results in skin-testing programs. Limits inherent in any diagnostic test employed under low-prevalence conditions explain why the TST probably gives more false than true positives in most places in the United States, says John Bass, MD, chair of the department of internal medicine at the University of Alabama at Birmingham.

Fordham Von Reyn, professor of medicine at Dartmouth Medical School in Hanover, NH, presented new and still unpublished evidence that quantifies how, in three sites scattered around the country, cross-reactions with atypical mycobacterial infections appear to account for an increasing number of positive TST results.

At the end of the IOM sessions, Columbia University medical ethicist Ron Bayer, PhD, made a closing statement that seemed to reflect the effects of the accumulated testimony accurately. He had gone to the hearings ready to give unions and other OSHA partisans the benefit of the doubt and to support the "little guy," Bayer reportedly told the audience. But the accumulated weight of evidence had worn down his resolve. Now, he said, he was ready to switch sides.