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Epi Seminar Series |
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Tuesday, May 19, 2009
Health Sciences K069
3:30 to 4:50pm
The use of survival methods to describe risk of Methicillin-Resistant Staphylococcus aureus (MRSA) infection in King County, Washington Jails
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Team Members:
Matthew Hanson, MD, DTM&H
Epidemic Intelligence Service Officer
Communicable Disease Epidemiology & Immunization Section
Public Health - Seattle & King County
Carla V. Rodriguez, MPH
Doctoral Student, Department of Epidemiology, University of Washington
Graduate Research Assistant, Communicable Disease Epidemiology & Immunization Section Public Health -Seattle & King County
Jeff Duchin, MD
Chief, Communicable Disease Epidemiology & Immunization Section Public Health -Seattle & King County
Associate Professor in Medicine, Division of Infectious Diseases, University of Washington
Adjunct Associate Professor in Epidemiology, School of Public Health, University of Washington
Tao Kwan-Gett, MD
Medical Epidemiologist
Public Health Seattle and King County
Abstract:
Methicillin-Resistant Staphylococcus aureus Infection in a Washington Prison System
Background: Recent media reports of MRSA infections in hospitals and prisons have alarmed the public. In 2007, Public Health Seattle & King County established a surveillance system in two King County, Washington, jails to describe risk of MRSA infection in an institutional setting. Surveillance activities include monthly reports of case investigations and prevalence, and quarterly and annual reports that also describe incidence of disease. We conducted a retrospective cohort study to describe whether the risk of potentially jail acquired MRSA increased over time.
Methods: The population at risk included all inmates incarcerated in 2008. MRSA events were identified from laboratory results in the jail electronic health record (EHR) and a commercial laboratory serving the jail. The time interval of interest is time since booking (jail entry) to MRSA onset or jail release. Where ‘onset date’ was not available, culture date was used as a proxy. MRSA events are unique for each incarceration, although persons are not unique in the dataset. To represent potentially jail-acquired infections, analysis of time to MRSA symptom onset or release began at day 15 after booking. Non-parameteric survival methods were used to estimate the instantaneous risk of MRSA infection in an incarcerated population, adjusting for repeated observations. Inmate-days were provided by jail census data.
Results: 234 infections were observed among 50,599 incarcerations. Fifty-five percent of infections (n=129) occurred within 15 days of incarceration. The risk of MRSA appears not to be increasing over time, and consistent with a constant hazard, after adjusting for repeated observations. The crude incidence estimated from the baseline instantaneous risk of MRSA infection is 0.93 cases per 10,000 person-days (95%CI: 0.74, 1.16), adjusting for repeat observations. A 2% increased risk per year in age was found to be significant in this population (HR: 1.02, 95% CI: 1.01, 1.04). No differential risk was found by sex, race or jail location. Proportional hazards assumptions were met.
Conclusions: Risk for MRSA appears constant over time in a jail setting. Only age, not jail location, race or sex, is associated with differential risk for infection. Results were similar in an analysis that delayed study entry by 5 days.
Suggested Reading Material: Meticillin-resistant Staphylococcus aureus among US prisoners and military personnel: review and recommendations for future studies
Speaker's Bio: Carla Rodriguez is a 3rd year doctoral student in the Department of Epidemiology, University of Washington. She has spent 10 years working in applied research at the city health departments of New York City, San Francisco and Seattle/King County. Over the last 6 years, she has specifically worked on projects related to infectious disease surveillance. She is currently a graduate research assistant with the Communicable Disease Epidemiology and Immunization Section, Public Health – Seattle & King County (PHSKC).
PHSKC is the 10th largest metropolitan health department in the United States. PHSKC employs 1900 staff in 39 sites with an annual budget of $296 million. The goals of the department include disease control, communicable disease epidemiology and immunizations, and environmental health protection. Health promotion functions include education programs geared towards preventing behaviors that lead to disease, averting injuries and managing chronic health conditions. Health provision functions include convening and leading system-wide efforts to improve access and quality, advocating for access to quality health care for all, forming partnerships with service providers and directly providing individual health and emergency services when there is a public health need, including correctional health services, The department serves a resident population of 1.8 million people in large and diverse geographic area, with 19 acute care hospitals and over 7000 medical professionals, where over 50 languages are spoken. Approximately 30 million annual visitors add to the population for which services are provided. SAVE PUBLIC HEALTH!
Light refreshments will be served.
For more information - please contact Ann Vander Stoep, PhD
Updated on July 2, 2009