Nasal Decolonization and Polymerase Chain Reaction Screening in the Intensive Care Unit: Friend or Foe?

In this issue of the journal, Ito et al report a retrospective study assessing the clinical value of nasal polymnerase chain reaction (PCR) screening for the detection of methicillin-resistant Staphylococcus aureus (MRSA) colonization in an intensive care unit (ICU) setting where a universal decolonization strategy is implemented. Their main message is that the negative predictive value (NPV) of nasal PCR remains clinically useful even when the test is performed up to 1 week after the empirical initiation of decolonization. The authors should be commended for addressing a clinically relevant and methodologically challenging question and for navigating the delicate balance between diagnostic stewardship and infection prevention. Staphylococcus aureus accounts for more than 10% of infections in ICUs, although in most settings, no more than one-third of these infections are caused by MRSA strains [1]. In a recent meta-analysis, the combined prevalence of nasal and/or pharyngeal colonization by S. aureus was 26.4%, and MRSA accounted for 15.0% of colonizing strains [2]. However, whether the nose alone represents an adequate sentinel site for colonization in routine clinical practice remains open to debate, as several studies suggest that between 9% and 33% of carriers may be missed when only nasal screening is performed [3].