Methicillin-resistant Staphylococcus aureus (MRSA) screening upon inpatient hospital admission: Is there concordance between nasal swab results and samples taken from skin and soft tissue?

Abstract

Background: Methicillin-resistant Staphylococcus aureus (MRSA) infections are associated with increased mortality and healthcare costs. In 2007, a Veterans' Affairs (VA) hospital implemented a MRSA nasal screening program, following a nationwide VA mandate, in an effort to reduce healthcare-associated MRSA infections. Objective: To evaluate the correlation between the nasal screening results for MRSA and culture results of wound and tissue sites. Methods: This retrospective study was conducted on inpatients at our VA hospital. Patients were included if they had undergone nasal screening for MRSA plus culture of a wound or tissue site within 30 days of hospital admission. Results: In total, 337 patients underwent nasal screening and wound culture and 211 underwent nasal screening and wound and tissue cultures. The prevalence of MRSA nasal colonization was 14.2% for wound samples and 15.2% for tissue samples. The sensitivities of MRSA nasal screening for detecting MRSA were 64.6% for wound cultures and 65.5% for tissue cultures. Specificities were 86.2% and 88.8% for wound and tissue cultures, respectively. The positive predictive values (PPVs) were 43.7% and 51.2% for wound and tissue cultures, respectively, and the negative predictive values (NPVs) were high at 93.6% and 93.5%, respectively. Conclusions: In cases of wound or tissue samples for which culture results are pending, a negative MRSA nasal swab may be a component of the decision to withhold or discontinue MRSA-active agents.