MRSA nasal PCR as a prevalence-dependent stewardship tool in hospitalized children: a structured review

Introduction Empiric anti-methicillin-resistant Staphylococcus aureus (MRSA) therapy is common in hospitalized children with severe pneumonia or suspected sepsis. MRSA nasal polymerase chain reaction (PCR) is increasingly used to support de-escalation, but its central metric, the negative predictive value (NPV), is often quoted without the prevalence on which it depends.Areas covered PubMed, EMBASE, and the Cochrane Library were searched from January 2018 to April 2026. Twenty-seven sources were synthesized; the pediatric diagnostic-accuracy and stewardship studies and the in-window meta-analyses were appraised with QUADAS-2, EPOC, or AMSTAR-2. We examine why NPV is high in children, the prevalence above which a negative swab no longer rules out infection, performance by syndrome, and the pediatric implementation and cost literature, and propose a prevalence-conditioned framework for prospective evaluation.Expert opinion The pediatric evidence is observational, and no study was designed to test whether PCR-guided de-escalation is safe. A negative swab is a defensible rule-out aid in severe or complicated pneumonia and selected low-prevalence intensive care sepsis, but not in skin, soft-tissue, or osteoarticular infection. Because NPV depends on prevalence, programs should measure the proportion of children with the target syndrome who have culture-confirmed MRSA infection locally before applying a published NPV.