Background: Methicillin-resistant Staphylococcus aureus (MRSA) infections continue to be a leading problem in health care facilities worldwide. Methods: This single-center retrospective cohort study consisted of a derivation phase and a validation phase. The derivation phase included all patients admitted to Osaka University Hospital between May 2010 and April 2011. We proposed a provisional available, bed-sided, comprehensive (ABC) score, and evaluated its accuracy using the clinical diagnosis as a reference. We subsequently revised ABC scores based on k coefficient scores of each variable this revision was validated by applying it to another patient population. Results: A total of 172 patients and 154 cases were enrolled in the derivation and validation studies, respectively. The revised ABC score consisted of four simple variables: type of clinical specimen (1 to 3 points), Gram-staining result (1 point), presence of local inflammation (2 points), and a systemic inflammatory response (2 points). A revised score of ≥5 points was sensitive (93.8%) and specific (90.6%), and the area under the receiver-operating curve was 0.969 (95% CI
0.957-1). Conclusions: We developed a simple and comprehensive scoring system for diagnosis of nosocomial MRSA infections
this system is applicable in a wide variety of situations.