Infection Control & Hospital Epidemiology

Original Article

Quantifying the Impact of Extranasal Testing of Body Sites for Methicillin-Resistant Staphylococcus aureus Colonization at the Time of Hospital or Intensive Care Unit Admission

James A. McKinnella1a2 c1, Susan S. Huanga3, Samantha J. Eellsa1, Eric Cuia3 and Loren G. Millera1

a1 Infectious Disease Clinical Outcomes Research Unit, Division of Infectious Disease, Los Angeles Biomedical Research Institute, Harbor-UCLA Medical Center, Torrance, California

a2 Torrance Memorial Medical Center, Torrance, California

a3 Division of Infectious Diseases and Health Policy Research Institute, University of California, Irvine, School of Medicine, California


Objective. Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of healthcare-associated infections. Recent legislative mandates require nares screening for MRSA at hospital and intensive care unit (ICU) admission in many states. However, MRSA colonization at extranasal sites is increasingly recognized. We conducted a systematic review of the literature to identify the yield of extranasal testing for MRSA.

Design. We searched MEDLINE from January 1966 through January 2012 for articles comparing nasal and extranasal screening for MRSA colonization. Studies were categorized by population tested, specifically those admitted to ICUs and those admitted to hospitals with a high prevalence (6% or greater) or low prevalence (less than 6%) of MRSA carriers. Data were extracted using a standardized instrument.

Results. We reviewed 4,381 abstracts and 735 articles. Twenty-three articles met the criteria for analysis (n = 39,479 patients). Extranasal MRSA screening increased the yield by approximately one-third over nares alone. The yield was similar at ICU admission (weighted average, 33%; range, 9%–69%) and hospital admission in high-prevalence (weighted average, 37%; range, 9%–86%) and low-prevalence (weighted average, 50%; range, 0%–150%) populations. For comparisons between individual extranasal sites, testing the oropharynx increased MRSA detection by 21% over nares alone; rectum, by 20%; wounds, by 17%; and axilla, by 7%.

Conclusions. Extranasal MRSA screening at hospital or ICU admission in adults will increase MRSA detection by one-third compared with nares screening alone. Findings were consistent among subpopulations examined. Extranasal testing may be a valuable strategy for outbreak control or in settings of persistent disease, particularly when combined with decolonization or enhanced infection prevention protocols.

(Received August 13 2012)

(Accepted September 21 2012)


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