PHILADELPHIA -- For workers on the front lines of the battle with H1N1 pandemic flu, the retraction of a study on protective masks adds to the confusion over how to guard against infection, experts said.
Two recent studies have looked at the issue and -- until this weekend -- were split on the results, according to Andrew Pavia, MD, of the University of Utah, chair of the pandemic flu task force for the Infectious Diseases Society of America.
The retracted study -- conducted in China by Australian researchers -- originally suggested that the expensive N95 respirators were effective and offered better protection than standard surgical masks.
On the other hand, a Canadian study found no difference between the two masks. (See IDSA: N95 versus Surgical Mask Findings Retracted)
Many healthcare workers may still think "the score is one to one," Pavia told 鶹ý. But, in fact, "it's 0 and 2, with no evidence of a benefit" for N95 respirators, he said.
Researchers here at the annual meeting of the infectious diseases society were startled when the Australian researchers said their original analysis was in error, and they could not demonstrate a benefit for the N95 masks.
After a reanalysis prompted by questions from peer reviewers, the findings no longer demonstrated a significant benefit for the N95 respirators, reported Holly Seale, PhD, of the University of New South Wales in Sydney, Australia.
Pavia said there was "dismay that the perception remains out there that this study showed something that it didn't show."
There was "a little bit of shock" that the results had changed so dramatically, said Neil Fishman, MD, of the University of Pennsylvania, president-elect of the Society for Healthcare Epidemiology of America.
The two societies have consistently argued that N95 respirators are not the best way to guard against H1N1 infection and that their use has serious detrimental effects in terms of costs, patient care, and side effects for healthcare workers.
A committee of the infectious diseases society met the morning after the retraction to discuss the issue, according to Robert Guidos, JD, the society's vice-president for public policy and governmental affairs.
"The evidence is now even more supportive of our position," Guidos told 鶹ý, adding the retraction is likely to create "greater confusion" among healthcare workers.
But the two societies were undercut by the original Australian study results, and most experts think those results influenced an Institute of Medicine recommendation that N95 respirators be used. (See IOM Panel Hears How to Protect Healthcare Workers from H1N1)
The lead author of the study, C. Raina MacIntyre, PhD, also of the University of New South Wales, presented the preliminary findings to the institute even before their first public presentation. (See ICAAC: Surgical Masks Don't Prevent Infection)
On the other hand, the Canadian study -- published in the Journal of the American Medical Association in October -- was not part of the evidence considered by the IOM panel.
The institute's panel "did not necessarily get all of the appropriate data," Pavia said.
The episode illustrates the danger of making policy based on preliminary studies, he said.
"Everything at a meeting like this has to be considered somewhat preliminary," he said. "You can't draw real conclusions from 12 slides."
The "good news," Pavia said, is that the peer review process forced the researchers to reconsider their data and change their conclusions.
But "detrimental consequences" remain, according to Fishman, including the following:
- CDC guidance suggesting the respirators be used
- The cost of complying with the guidance
- Side effects of wearing N95 respirators
- Adverse effects on patient care associated with the extra level of protection
The CDC guidance -- which does not mention the IOM panel report -- urges the use of masks "at least as protective as a fit-tested disposable N95 respirator for healthcare personnel who are in close contact with patients with suspected or confirmed 2009 H1N1 influenza."
It says the basis for the recommendation is "the unique conditions associated with the current pandemic."
The agency did not immediately respond to a request for comment.
The guidance has several drawbacks, Pavia said, including the cost. Depending on variables such as the size of an order, a single N95 respirator costs about $4, he said, while surgical masks are "several for a dollar."
Supply is also limited, which may mean the masks are harder to come by for applications where evidence supports their use, such as for protection against tuberculosis.
Healthcare workers may find the N95 masks difficult to use, Pavia added, and there's evidence of such adverse effects as headache, sore noses, and difficulty breathing.
In addition, he said several studies have shown that when healthcare workers must use such protection, they tend to give less care to patients. "It's a downside we're acutely aware of," he said.