Infections caused by methicillin-resistant Staphylococcus aureus doubled at academic medical centers in the U.S. between 2003 and 2008, according to a report.
Researchers from the University of Chicago Medicine and the University HealthSystem Consortium estimate hospitalizations increased from about 21 out of every 1,000 patients hospitalized in 2003 to about 42 out of every 1,000 in 2008, or almost one in 20 inpatients.
"The rapid increase means that the number of people hospitalized with recorded MRSA infections exceeded the number hospitalized with AIDS and influenza combined in each of the last three years of the survey: 2006, 2007 and 2008," Michael David, MD, PhD, a study author and an assistant professor of medicine at the University Chicago, said in a news release.
The findings run counter to a recent CDC study that found MRSA cases in hospitals were declining, the authors noted. The CDC study looked only at cases of invasive MRSA (infections found in the blood, spinal fluid or deep tissue). It excluded infections of the skin, which the UHC study includes.
The researchers attributed much of the overall increase they detected to community-associated infections. When MRSA first emerged, it was primarily contracted in hospitals or nursing homes. "Community-associated MRSA infections, first described in 1998, have increased in prevalence greatly in the U.S. in the last decade," David said. "Meanwhile, healthcare-associated strains have generally been declining."
The study utilized the UHC database, which includes data from 90% of all not-for-profit academic medical centers in the U.S. However, like many such databases, the UHC data are based on billing codes that hospitals submit to insurance companies, which often underestimate MRSA cases.
For example, according to the researchers, hospitals might not report MRSA cases that do not affect insurance reimbursement for that particular patient. In other cases, hospitals might be limited in the number of billing codes they can submit for each patient, which can result in a MRSA code being left off the billing report if it was not among the primary diagnoses.
David and his team accounted for these errors by using detailed patient observations from the University of Chicago Medical Center and three other hospitals. They looked at patient records to find the actual number of MRSA cases in each hospital over a three-year period. The researchers then checked the insurance billing data to see how many of those cases were actually recorded. They found that the billing data missed a third to half of actual MRSA cases at the four hospitals. They used that rate of error as a proxy to correct the billing data from the 420 other hospitals in the UHC database and arrive at the final estimates.
"I think this is still an underestimate of actual cases," David said. "But we can say with some assurance that this correction gives us a more accurate lower bound for how many [MRSA] cases there actually are. What’s clear from our data is that cases were on the rise in academic hospitals in 2003 to 2008."
The study is scheduled for publication in the August issue of Infection Control and Hospital Epidemiology, the journal of the Society of Healthcare Epidemiology for America. The study abstract is available at http://1.usa.gov/ONr8Jx.
Researchers from the University of Chicago Medicine and the University HealthSystem Consortium estimate hospitalizations increased from about 21 out of every 1,000 patients hospitalized in 2003 to about 42 out of every 1,000 in 2008, or almost one in 20 inpatients.
"The rapid increase means that the number of people hospitalized with recorded MRSA infections exceeded the number hospitalized with AIDS and influenza combined in each of the last three years of the survey: 2006, 2007 and 2008," Michael David, MD, PhD, a study author and an assistant professor of medicine at the University Chicago, said in a news release.
The findings run counter to a recent CDC study that found MRSA cases in hospitals were declining, the authors noted. The CDC study looked only at cases of invasive MRSA (infections found in the blood, spinal fluid or deep tissue). It excluded infections of the skin, which the UHC study includes.
The researchers attributed much of the overall increase they detected to community-associated infections. When MRSA first emerged, it was primarily contracted in hospitals or nursing homes. "Community-associated MRSA infections, first described in 1998, have increased in prevalence greatly in the U.S. in the last decade," David said. "Meanwhile, healthcare-associated strains have generally been declining."
The study utilized the UHC database, which includes data from 90% of all not-for-profit academic medical centers in the U.S. However, like many such databases, the UHC data are based on billing codes that hospitals submit to insurance companies, which often underestimate MRSA cases.
For example, according to the researchers, hospitals might not report MRSA cases that do not affect insurance reimbursement for that particular patient. In other cases, hospitals might be limited in the number of billing codes they can submit for each patient, which can result in a MRSA code being left off the billing report if it was not among the primary diagnoses.
David and his team accounted for these errors by using detailed patient observations from the University of Chicago Medical Center and three other hospitals. They looked at patient records to find the actual number of MRSA cases in each hospital over a three-year period. The researchers then checked the insurance billing data to see how many of those cases were actually recorded. They found that the billing data missed a third to half of actual MRSA cases at the four hospitals. They used that rate of error as a proxy to correct the billing data from the 420 other hospitals in the UHC database and arrive at the final estimates.
"I think this is still an underestimate of actual cases," David said. "But we can say with some assurance that this correction gives us a more accurate lower bound for how many [MRSA] cases there actually are. What’s clear from our data is that cases were on the rise in academic hospitals in 2003 to 2008."
The study is scheduled for publication in the August issue of Infection Control and Hospital Epidemiology, the journal of the Society of Healthcare Epidemiology for America. The study abstract is available at http://1.usa.gov/ONr8Jx.
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