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The use of aggregated hospital antimicrobial susceptibility data (antibiograms) can be valuable for monitoring regional susceptibility patterns. However, limitations exist, including consistency of reporting and data quality. The Clinical and Laboratory Standards Institute (CLSI) publishes guidelines for antimicrobial susceptibility testing and antibiogram standardization. Standardization allows for regional and state-wide susceptibility pattern analysis. The Massachusetts Department of Public Health (MDPH) conducted an evaluation to determine the extent to which microbiology laboratories followed CLSI guidelines for antibiogram generation from 2002 to 2010.
METHODS:
MDPH requests antibiograms from acute-care facilities in Massachusetts annually. Antibiograms received are verified, entered into a Microsoft Access database and analyzed using SAS v9.2 (SAS Institute Inc., Cary, NC, USA). Adherence to five CLSI recommendations was evaluated: (1) exclusion of duplicate bacterial isolates; (2) formatting of data into a grid; (3) separate reporting of Staphylococcus aureus isolates by methicillin (oxacillin)-susceptibility; (4) reporting of species only when 30 or more isolates are tested annually; and, (5) summarizing data by patient type. Recommendations 1-3 were first made by CLSI in 2002 and the remainder in 2005.
RESULTS:
An average of 54 antibiograms from 71 acute-care facilities were received per year during the study period (76% response rate). 1) Exclusion of duplicate bacterial isolates increased from 67% in 2005 to 93% in 2008 and has remained constant. 2) In 2002, antibiograms received by MDPH ranged from printed multi-page reports to large poster-size formats. By 2010, approximately 80% of submitted antibiograms were in a one-page grid format, consistent with the CLSI recommendation. 3) Separate reporting of S. aureus susceptibilities increased from 20% in 2002 to 50% in 2010. 4) In 2010, 57% of hospitals reported organisms that were isolated fewer than 30 times per year, a decrease from 86% of hospitals in 2002. 5) Between 2002 and 2010, 22-31% of hospitals reported inpatient isolates only. Approximately 63-78% of hospitals reported all patient isolates. Less than 10% of hospitals reported ICU isolate data separately.
CONCLUSIONS:
Prior to 2002, little guidance was available to assist hospital microbiology laboratories in generating antibiograms. Since then, CLSI has published three documents promoting standards-based antibiogram presentation. Massachusetts observed an increase in compliance with these recommendations, however variation among and even within hospitals continues. Given the importance of monitoring emerging trends in antibiotic resistance, clinical microbiology laboratories would best follow recommended reporting procedures for standardized analysis. Until then, the lack of data standardization must be considered when assessing regional antimicrobial resistance patterns.