Reanalysis changes findings in respiratory protection study

[indigo girl]

http://www.cidrap.umn.edu/cidrap/content/influenza/swineflu/news/nov0509respirator.html

What a mess. It looks like Dr. McIntyre still believes that her study correctly shows the superiority of the N95 to the surgical mask. Too bad she was not present to defend her research. SHEA is determined to get rid of the N95 as the routine protection. SHEA is also saying that this study influenced the IOM decision but because it was not yet published, McIntyre who was on that committee says it did not. IOM only looked at published studies.

Better read the whole article to make sense of this. SHEA probably won't give up until they get OSHA and CDC to change the level of protection.

Raina MacIntyre and colleagues first presented their findings at a medical conference in mid-September, reporting that N-95s, compared with no respiratory protection, reduced the risk of confirmed influenza in hospital workers by 75%, whereas surgical masks had no protective effect. The findings were hailed by some experts as a landmark in a field where few clinical studies have been done.

But at the Infectious Diseases Society of America (IDSA) annual meeting last week, MacIntyre's team presented a new analysis of their data, made at the request of peer reviewers. The reanalysis excluded the control group of unprotected workers. The result was that workers who wore N-95s still appeared to be better off than those with surgical masks, but the differences were no longer statistically significant.

Some press reports and critics of the study—which has not yet been published in a journal—characterized the reanalysis as a retraction of the earlier report. Critics also suggest that the study influenced the recent recommendation by the Institute of Medicine (IOM) that healthcare workers should wear N-95s when caring for H1N1 patients. MacIntyre was a member of the committee that wrote the IOM report, issued in September.

But MacIntyre says the reanalysis was not a retraction. She asserts that the study results still indicate a real difference in levels of protection, but the changes requested by the peer reviewers left the study "underpowered" to show significance. Further, she says the IOM panel considered only published studies in making its recommendations.

(hat tip FlaMedic)

[lamazeteacher]

Why does the study have to be published, to be valid?

Surgical type masks have never been considered effective for periods of time longer than 10 minutes, yet the ritual of using them in surgery, for hours, continues. When they are saturated with moisture from exhaling, microbes are sprayed outside them each time the wearer exhales.......

[indigo girl]

Why does the study have to be published, to be valid?

Surgical type masks have never been considered effective for periods of time longer than 10 minutes, yet the ritual of using them in surgery, for hours, continues. When they are saturated with moisture from exhaling, microbes are sprayed outside them each time the wearer exhales.......

I think the point was that her research did not influence the IOM decision to recommend the N95 as being the safest mask to prevent the wearer from being infected with an ILI. Since IOM based the decision only on published studies therefore SHAE cannot use her unpublished research as an excuse to pressure CDC into using changing the guidelines.