Methicillin Resistant Staphylococcus Aureus (MRSA) Bloodstream Infections
Data Methodology & Preliminary Report
In 2008, the South Carolina Department of Health and Environmental Control (DHEC) made Methicillin Resistant Staphylococcus Aureus Bloodstream Infections (MRSA BSI) a laboratory reportable condition. For the Hospital Infections Disclosure Act, a MRSA BSI is defined as a hospital acquired infection when a blood culture collected more than 72 hours after admission becomes positive for MRSA.
DHEC collects MRSA BSI data in three ways: (i) Electronic Laboratory Reporting (ELRs), (ii) disease report cards mailed to DHEC, (iii) or reports entered directly through Carolinas Health Electronic Surveillance System (CHESS). ELRs import directly into CHESS, and results submitted by disease report cards are manually entered into CHESS.
Once the data is in CHESS, a query is run that looks for all MRSAs that have blood listed as the specimen source. Blood specimen source options for MRSA are whole blood arterial or venous, and very rarely cord blood. Many times, there will be several labs for one person, but that does not translate into a person having multiple infections. If there are fourteen (14) or more days between the first blood draw and the subsequent blood draw, then the latest blood draws are counted as a new infection (event). For example, if a person has their first lab drawn on January 1st and another January 6th and a third one on January 9th, those are all considered the same event and not counted as multiple events. However if a person has their first lab on January 1st and another January 6th and a third on January 27th, the person would be listed as having two events.
After all of the MRSA BSIs have been pulled from CHESS, DHEC gives the file to the Office of Research and Statistics (ORS), where data from DHEC is run through the ORS unique identification system to obtain a unique identifier for linkage to health databases. Unique numbers replace personal identifiers and enables staff to “link across” multiple providers and settings while protecting confidentiality. The data linkage project was approved by the South Carolina Data Oversight Council. The ORS health databases include hospital uniform billing data for inpatient admissions, emergency department visits and outpatient surgeries. The ORS searches health data for encounters one year before and after the event date.
Once the data has been matched, ORS determines whether or not the MRSA BSI is a possible hospital acquired infection (HAI) or a community acquired infection (CA – MRSA). For January 2008 – October 2008 data, the following statistics were derived from the data:
- 557 infections in the DHEC file collected from 531 individuals.
- 357 were collected during an inpatient admission or emergency department visit.
- 278/357 (77.9%) were categorized as CA – MRSA infections.
- 79/357 (22.1%) were categorized as possible HAIs.
- At this time, data is preliminary and the match for the year is incomplete, so individual hospital data cannot be given at this time.