Open Access Highly Accessed Research article

Development and validation of a bedside risk score for MRSA among patients hospitalized with complicated skin and skin structure infections

Marya D Zilberberg12*, Paresh Chaudhari3, Brian H Nathanson4, Rebecca S Campbell5, Matthew F Emons5, Suzanne Fiske5, Harlen D Hays5 and Andrew F Shorr6

Author Affiliations

1 EviMed Research Group, LLC, Goshen, MA, USA

2 School of Public Health and Health Sciences, University of Massachusetts, Amherst, MA, USA

3 Astellas Pharma US, Inc, Deerfield, IL, USA

4 OptiStatim LLC, Longmeadow, MA, USA

5 Cerner Corporation, Beverly Hills, CA, USA

6 Washington Hospital Center, Washington, DC, USA

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BMC Infectious Diseases 2012, 12:154  doi:10.1186/1471-2334-12-154

Published: 11 July 2012

Abstract

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is a frequent cause of complicated skin and skin structure infections (cSSSI). Patients with MRSA require different empiric treatment than those with non-MRSA infections, yet no accurate tools exist to aid in stratifying the risk for a MRSA cSSSI. We sought to develop a simple bedside decision rule to tailor empiric coverage more accurately.

Methods

We conducted a large multicenter (N=62 hospitals) retrospective cohort study in a US-based database between April 2005 and March 2009. All adult initial admissions with ICD-9-CM codes specific to cSSSI were included. Patients admitted with MRSA vs. non-MRSA were compared with regard to baseline demographic, clinical and hospital characteristics. We developed and validated a model to predict the risk of MRSA, and compared its performance via sensitivity, specificity and other classification statistics to the healthcare-associated (HCA) infection risk factors.

Results

Of the 7,183 patients with cSSSI, 2,387 (33.2%) had MRSA. Factors discriminating MRSA from non-MRSA were age, African-American race, no evidence of diabetes mellitus, cancer or renal dysfunction, and prior history of cardiac dysrhythmia. The score ranging from 0 to 8 points exhibited a consistent dose–response relationship. A MRSA score of 5 or higher was superior to the HCA classification in all characteristics, while that of 4 or higher was superior on all metrics except specificity.

Conclusions

MRSA is present in 1/3 of all hospitalized cSSSI. A simple bedside risk score can help discriminate the risk for MRSA vs. other pathogens with improved accuracy compared to the HCA definition.

Keywords:
Skin infection; Prediction rule; Clinical decision; MRSA; Hospitalization