Nov 17, 2008 (CIDRAP News) – A Canadian study raises questions about the value of formal "fit testing" for the respirators worn by healthcare workers to protect them from airborne pathogens, suggesting that it does little good for workers who don't routinely wear the devices.
In the study, 44% of a sample of healthcare workers (HCWs) who lacked experience with respirator-fit testing managed to don the respirators properly, so that they formed a tight seal around the face, before they received any specific instructions.
After all the HCWs were trained in how to wear the equipment, testing showed that 74% of them had a good fit. But when the workers were asked to strap on respirators again 3 months later, only about 47% of them achieved a good fit—not significantly more than did so before they were trained.
"The utility of fit testing among infrequent users of N95 respirators is questionable," says the report, written by a team from the University of Alberta and the University of Saskatchewan, with M.C. Lee, MD, as first author. It was published online recently by Infection Control and Hospital Epidemiology and is scheduled for the December print edition.
In October 2006 the Department of Health and Human Services (HHS) issued interim guidance saying that the use of N-95 respirators—designed to stop 95% of small airborne particles—is "prudent" for medical workers providing any direct care for patients ill with confirmed or suspected pandemic influenza and is recommended in caring for those with pneumonia. HHS also said respirator use is prudent for support workers in direct contact with patients. Respirator manufacturers recommend fit testing for the devices.
However, Lee and colleagues write that respirator-fit testing is time-consuming and costly, and its long-term effectiveness in a healthcare setting has never been examined. They sought to determine whether an acceptable respirator seal could be achieved without training or fit testing, whether training and fit testing could ensure a good seal during later use, and whether HCWs who use respirators regularly can achieve a good seal more consistently.
Success without training
The researchers recruited 58 HCWs who had no experience with fit testing. They were first asked to put on a 3M 8210 N-95 respirator without any instruction, after which they underwent a fit test. Of the 43 HCWs who completed the study, 19 (44.2%) passed the fit test. Counting those who later dropped out of the study, 28 of 58 (48%) passed the test.
Next, all the volunteers received formal training in donning and adjusting the 8210 respirators, and then underwent another fit test. At that point another 13 workers passed the test, for a total of 32 of 43 (74.4%). Those who couldn't get an effective seal with the 8210 model were successfully fitted with other 3M respirators—ten with the 8110 model and one with the 9210. After achieving a proper fit, the volunteers were advised to remember which model they used and to choose the same one in the future.
The researchers invited the participants back 3 and 14 months after the initial testing and training and repeated the donning and testing steps. At 3 months, 20 of the 43 HCWs (46.5%) passed the test; this increased to 28 of 43 (65.1%) at 14 months. Neither rate was significantly better than the first pretraining rate. Further, neither passing the test the first time nor occasionally using a respirator afterward correlated with passing at 3 or 14 months.
If a volunteer chose the wrong respirator at 3 or 14 months, this was recorded as a failed attempt, and he or she was reminded which model had worked for him or her previously. Many of the volunteers could not recall which respirator to use, and many did not seem to recognize that fit is specific to respirator type, the report says.
Only a minority of the workers remembered and performed all five prescribed steps in donning a respirator, and fewer than 5% passed all the fit-test challenges, the article says. When the investigators assessed execution of the five steps individually in relation to the overall pass rate, they found evidence that two steps—"correct strapping" and "adjusting bridge of the nose correctly"—were important for achieving a good seal.
To assess whether frequent respirator use led to a more consistent fit, the researchers recruited 11 nurses working in a tuberculosis unit, all of whom had been tested before and used respirators daily. The nurses were tested three times at 2-week intervals, with no instruction the first two times. The third time, they were reminded of the standard fit-checking steps.
Four of the 11 nurses failed the first two tests; it was determined that all four were using the wrong model of respirator, despite previous fit testing. Two of them had lost significant weight since their earlier fit test. All four subsequently achieved a good fit with other respirator models.
The investigators also found that HCWs' confidence in their ability to pass a fit test did not correlate with actual test results. "HCWs cannot tell with any accuracy whether they have achieved an adequate facial seal after donning their respirator," they write.
Finding the right model
Noting that 48% of the untrained volunteers achieved a good fit with the 8210 respirator the first time, and that this increased to 74% after training, the authors write, "Our data suggest that fit testing may be most useful for the initial screening of people whose facial features preclude the use of the most common types of respirators (which, in our region, was the model 3M 8210 respirator)."
They also say their findings "challenge the current strategy for fit testing, which, in our region, is mandated every two years for all HCWs with direct patient care responsibility. Our findings question the need for fit testing of HCWs who utilize respirators on a frequent (ie, daily) basis, because their success rates were very high."
But for workers who seldom use respirators, different strategies may be needed, such as different teaching techniques or reminder sessions two or three times a year, because pass rates of 50% to 75% are "suboptimal," the article says.
The authors say the limitations of their study include its small sample size and the use of qualitative rather than quantitative fit testing. Qualitative fit testing depends on the ability of the wearer to taste or smell a noxious agent and therefore is not foolproof, they note.
An infection control expert's view
Eddie Hedrick, MT, emerging infections coordinator for the Missouri Department of Health and Senior Services, said the study seems to support doubts the infection control community has long had about the worth of fit testing.
"I think the study was designed pretty well," Hedrick said. "The biggest problem, as they say, is the small sample size. It's hard to translate that and say it's a definitive study. It creates more questions about the science behind the effectiveness of fit testing."
In the United States, hospitals are generally required to conduct annual respirator-fit testing for all employees who have exposure to airborne pathogens, which usually means anyone who has contact with patients, he said. Although a fit test itself takes only a few minutes, it probably takes a worker an hour or more to go get the test done and return to his or her work area, he added.
Hedrick chaired a panel of the Association for Professionals in Infection Control and Epidemiology (APIC) back in 1990 when the US Occupational Safety and Health Administration (OSHA) began moving toward requiring more sophisticated respiratory protection for HCWs. Until that time, workers had relied mostly on simple surgical masks, he said.
The effectiveness of fit testing has been questioned for years, Hedrick said. "If I fit-test someone and they go to the floor and don't use this [respirator] for a long time, and they suddenly get a TB patient and they put it on, if they don't put it on properly or check it, or if their face is contorted because they're laughing or smiling, then air goes around it. So the effectiveness has been questioned from day 1. One would think it might be worse sometimes than a surgical mask."
He said fit testing can mislead health workers about their safety. "A lot people when they put them on, they say, 'Well, I fit-tested it last year, so I'm OK.' So it's a false sense of security, and I think this study showed that."
That's why APIC emphasizes "fit checking," Hedrick explained. "We've always said, make sure when you put it on that it's molded to your face properly. That's better than waiting till January and then testing it."
He said it's important to make a good scientific case for fit testing, just as it is for other healthcare practices.
"We like to justify the efficacy of whatever we're asking people to do," he said. "If you do that, it's an easy sell. Just saying, 'If you don't do it, OSHA is going to get you,' isn't going to help."
Lee MC, Takaya S, Long R, et al. Respirator-fit testing: Does it ensure the protection of healthcare workers against respirable particles carrying pathogens? Infect Control Hosp Epidemiol 2008 Dec;29(12) (early online publication) [Abstract]
Nov 16, 2006, CIDRAP News story "Clinicians raise questions about respirator use in pandemic"
Oct 18, 2006, CIDRAP News story "HHS backs respirator use in caring for pandemic flu patients"
HHS's "Interim Guidance on Planning for the Use of Surgical Masks and Respirators in Health Care Settings during an Influenza Pandemic"