Selective methicillin-resistant Staphylococcus aureus (MRSA) screening programs target high-risk populations. To characterize high-risk populations, we conducted this systematic review to identify patient-level factors associated with MRSA carriage at hospital admission.

Studies were identified in the MEDLINE (1950-2011) and EMBASE (1980-2011) databases. English studies were included if they examined adult populations and used multivariable analyses to examine patient-level factors associated with MRSA carriage at hospital admission. From each study, we abstracted details of the population, the risk factors examined, and the association between the risk factors and MRSA carriage at hospital admission.

Our electronic search identified 972 citations, from which we selected 27 studies meeting our inclusion criteria. The patient populations varied across the studies. Ten studies included all patients admitted to hospital, and the others were limited to specific hospital areas. MRSA detection methods also varied across studies. Ten studies obtained specimens from the nares only, whereas other studies also swabbed wounds, catheter sites, and the perianal region. Methods of MRSA diagnoses included polymerase chain reaction tests, cultures in various agar mediums, and latex agglutination tests. Patient age, gender, previous admission to hospital, and previous antibiotic use were the risk factors most commonly examined. The risk factor definition and study methods varied among studies to an extent that precluded meta-analysis.

The existing literature cannot be used to identify risk factors for MRSA colonization at the time of hospitalization. Future studies should be aware of the differences in the existing literature and aim to develop standardized risk factor definitions.