Calibrated Dichotomous Sensitivity (CDS)

The Calibrated Dichotomous Sensitivity (CDS) method was developed in Australia and is used in some laboratories. For more information about the development of the CDS method, see the CDS website. This method determines the antimicrobial susceptibility of organisms using agar disc diffusion. Calibrated disc antimicrobial quantities allow easy interpretation with dichotomous results of sensitive or resistant that align with the minimum inhibitory concentration (MIC) of the organism. The CDS method does not report intermediate or susceptible increased exposure categories.

The CDS microbiology results will list several antimicrobials proposed for use. Ideally, the narrowest spectrum antimicrobials are listed first (‘cascade reporting’), which limits the number of available therapeutic options. This selective reporting is a key antimicrobial stewardship principle and assists in limiting broad-spectrum antimicrobial prescribing.

Microbiological reports, in particular serological reports, may be accompanied by interpretative comments. These should guide interpretation and may assist in selection of the most appropriate antimicrobial at the most appropriate dose.