Development and validation of a bedside risk score for MRSA among patients hospitalized with complicated skin and skin structure infections.
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.
EviMed Research Group, LLC, Goshen, MA, USA. Evimedgroup@gmail.com
Marya D
MD
Zilberberg
Paresh
P
Chaudhari
Brian H
BH
Nathanson
Rebecca S
RS
Campbell
Matthew F
MF
Emons
Suzanne
S
Fiske
Harlen D
HD
Hays
Andrew F
AF
Shorr
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015510:Clinical Medicine / Q000379:methods*; D015331:Cohort Studies; D003661:Decision Support Techniques; D005260:Female; D006760:Hospitalization; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification*; D008875:Middle Aged; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013207:Staphylococcal Skin Infections / Q000175:diagnosis* / Q000382:microbiology* / Q000473:pathology; D014481:United States; D055815:Young Adult