Lewis J. Radonovich, MD; Bradley S. Bender, MD
Do surgical masks provide protection similar to the N95 respirator in health care workers (HCWs) at high risk for exposure to influenza?
Randomized controlled trial. ClinicalTrials.gov NCT00756574.
Blinded (laboratory personnel conducting assays, polymerase chain reaction [PCR], and viral cultures).*
Mean 98 days. The study was stopped early when the Ontario Ministry of Health and Long-Term Care recommended N95 respirators for all HCWs caring for patients with febrile respiratory illness.
7 emergency departments, 9 acute medical units, and 6 pediatric units in 8 tertiary care hospitals in Ontario, Canada.
446 nurses (mean age 36 y, 94% women) who were expected to work full-time (> 37 h/wk) on the study units and had current fit-test certification for the N95 respirator.
Use of surgical masks (n = 225) or N95 respirators (n = 221) when caring for patients with febrile respiratory illness at the start of the influenza season (i.e., ≥ 2 consecutive isolations of influenza virus per wk in each study region). Nurses also wore gloves and gowns when entering patients’ rooms.
Primary outcome was laboratory-confirmed influenza (detection of viral RNA using reverse-transcriptase PCR from nasopharyngeal and flocked nasal specimens or ≥ 4-fold increase in serum antibodies to circulating influenza strain antigens). Secondary outcomes included influenza-like illness (ILI) (cough and temperature ≥ 38° C), work-related absenteeism, and physician visits for respiratory illness.
95% (intention-to-treat analysis).
Nurses who used surgical masks did not differ from those who used N95 respirators for laboratory-confirmed influenza (Table); because the lower limit of the 95% CI for the risk difference was > −9%, the criterion for noninferiority was met. The mask and N95 respirator groups did not differ for secondary outcomes (Table).
Surgical masks were noninferior to the N95 respirator in preventing laboratory-confirmed influenza in health care workers at high risk for exposure.
Surgical masks vs N95 respirators for preventing influenza in health care workers†
†CI defined in Glossary.
‡Cough and temperature ≥ 38°C.
Radonovich LJ, Bender BS. Surgical masks were noninferior to N95 respirators for preventing influenza in health care providers. Ann Intern Med. ;152:JC3–2. doi: 10.7326/0003-4819-152-6-201003160-02002
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Published: Ann Intern Med. 2010;152(6):JC3-2.
Infectious Disease, Influenza, Pulmonary/Critical Care.
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