The Clinical Utility of Methicillin-Resistant Staphylococcus aureus (MRSA) Nasal Screening to Rule Out MRSA Pneumonia: A Diagnostic Meta-analysis With Antimicrobial Stewardship Implications

Background. Recent literature has highlighted methicillin-resistant Staphylococcus aureus (MRSA) nasal screening as a possible antimicrobial stewardship program tool for avoiding unnecessary empiric MRSA therapy for pneumonia, yet current guidelines recommend MRSA therapy based on risk factors. The objective of this meta-analysis was to evaluate the diagnostic value of MRSA nasal screening in MRSA pneumonia. Methods. PubMed and EMBASE were searched from inception to November 2016 for English studies evaluating MRSA nasal screening and development of MRSA pneumonia. Data analysis was performed using a bivariate random-effects model to estimate pooled sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Results. Twenty-two studies, comprising 5163 patients, met our inclusion criteria. The pooled sensitivity and specificity of MRSA nares screen for all MRSA pneumonia types were 70.9% and 90.3%, respectively. With a 10% prevalence of potential MRSA pneumonia, the calculated PPV was 44.8%, and the NPV was 96.5%. The pooled sensitivity and specificity for MRSA community-acquired pneumonia (CAP) and healthcare-associated pneumonia (HCAP) were 85% and 92.1%, respectively. For CAP and HCAP both the PPV and NPV increased, to 56.8% and 98.1%, respectively. In comparison, for MRSA ventilated-associated pneumonia, the sensitivity, specificity, PPV, and NPV were 40.3%, 93.7%, 35.7%, and 94.8%, respectively. Conclusion. Nares screening for MRSA had a high specificity and NPV for ruling out MRSA pneumonia, particularly in cases of CAP/HCAP. Based on the NPV, MRSA nares screening is a valuable tool for AMS to streamline empiric antibiotic therapy, especially among patients with pneumonia who are not colonized with MRSA.