ISO 13843:2017 deals with characterization of microbiological methods. In terms of ISO 13843:2017, characterization means the study of parameters that can be measured to describe how the method is likely to perform in a given set of conditions, which can be described as performance characteristics. ISO 13843:2017 describes procedures for the determination of performance characteristics which can be used for subsequent validation or verification of methods.

The emphasis is on selective quantitative methods and ISO 13843:2017 applies to all types of water. For methods that are not based upon direct microscopic count, colony count or most probable number, the applicability of the procedures described in ISO 13843:2017 should be considered carefully.