Many Australian laboratories are considering the adoption of European Committee on Antimicrobial Susceptibility Testing (EUCAST) disc diffusion method within their laboratories. Calibrated Dichotomous Sensitivity Testing (CDS) and Clinical Laboratory Standards Institute (CLSI) are the commonly used standards in Australia.
The aim of this study is to find if EUCAST is a suitable method for the Goulburn Valley Health Pathology (GVHP) laboratory with selection criteria such as cost, automation, reproducibility, accuracy and flexibility considered. CDS is the current method at GVHP and it is not calibrated to ISO standards.
EUCAST quality controls were performed for 20 non-consecutive days to find the reproducibility and the performance. The performance categorical agreement has shown that the reproducibility of both methods were ≥90%. This result was found using both the automated Adagio instrument and manual reading with calliper.
33 non-duplicate gram positive clinical isolates and 29 gram negative non-duplicate clinical isolates were compared for both CDS and EUCAST methods. AST verification studies showed that there was a good overall categorical agreement between these two methods (≥90%). The calculated combined major errors and minor errors were also <10%.
Performance results of the EUCAST method at GVHP has shown that there is a good reproducibility and the time it takes to perform the method is similar to CDS, though the CDS method is easier to perform. Adagio makes it easier to interpret EUCAST results but the cost of the instrument increases the cost per test. While the performance of EUCAST was satisfactory, other factors considered show CDS to be more suitable for GVHP. GVHP guidelines requirements for reporting antimicrobials meant in order to test all required discs, EUCAST and CDS would need to be run simultaneously increasing time and costs. Performing both CDS and EUCAST methods at GVHP may cause confusion to the staff, and also fail to meet the ASA goal of breakpoint harmonisation.