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Inclusion of 30-Day Postdischarge Detection Triples the Incidence of Hospital-Onset Methicillin-Resistant Staphylococcus aureus

Taliser R. Avery MS, Ken P. Kleinman ScD, Michael Klompas MD MPH, Ann Aschengrau ScD MS and Susan S. Huang MD MPH
Infection Control and Hospital Epidemiology
Vol. 33, No. 2 (February 2012), pp. 114-121
DOI: 10.1086/663714
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Page Count: 8
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Inclusion of 30-Day Postdischarge Detection Triples the Incidence of Hospital-Onset Methicillin-Resistant Staphylococcus aureus
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Background. Hospitalized patients are at increased risk for acquisition of methicillin-resistant Staphylococcus aureus (MRSA). As hospital length of stay shortens, hospital-acquired MRSA events may be more likely to be detected after discharge.Objective. We assessed the impact of attributing MRSA cases discovered within 30 days after discharge to the most recent hospitalization and identified patient characteristics associated with MRSA detection after discharge.Design. Retrospective cohort study.Setting. Twenty-seven acute care hospitals in Orange County, California.Participants. Adult acute care admissions (2002–2007).Methods. Using a countywide hospital data set containing diagnostic codes with present-on-admission (POA) indicators, we identified the first admission with a MRSA code for each patient. This incident MRSA admission was defined as predischarge-detected (pre-DD) hospital-onset MRSA (HO-MRSA) when MRSA was not POA. If MRSA was POA and a prior admission occurred within 30 days, this prior admission was assigned postdischarge-detected (post-DD) HO-MRSA. We evaluated the impact of including post-DD HO-MRSA in the calculation of hospital HO-MRSA incidence using signed-rank tests and reviewed changes in hospital rankings. We conducted multivariate comparisons of patient characteristics of pre-DD versus post-DD HO-MRSA patients.Results. Among 1,217,253 at-risk hospitalizations, the inclusion of post-DD HO-MRSA tripled the median hospital HO-MRSA incidence, from 12.2 to 35.7 cases per 10,000 at-risk admissions (). Hospital ranking changed substantially when including post-DD HO-MRSA. Patients with shorter stays were more likely to have post-DD MRSA.Conclusions. On the basis of administrative claims data, the inclusion of post-DD HO-MRSA significantly increased the estimated HO-MRSA incidence and altered hospital rankings. This finding underscores the limitations of single-facility data when deriving HO-MRSA incidence and rank.

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