What is ISO 16256 about?
ISO 16256 is one of a series of documents for clinical laboratory testing and in vitro diagnostic test systems and describes a method for testing the susceptibility to antifungal agents of yeasts, including Candida spp. and Cryptococcus neoformans, that cause infection. The reference method described here has not been used in studies of the yeast forms of dimorphic fungi, such as Blastomyces dermatitidis and/Histoplasma capsulatum variety capsulatum. Moreover, testing filamentous fungi (moulds) introduces several additional problems in standardization not addressed by the current procedure.
ISO 16256 describes the broth microdilution reference method, which can be implemented by either of two pathways. One pathway involves the visual determination of MICs (CLSI method), the second pathway involves the spectrophotometric determination of MICs (EUCAST method), The MIC reflects the activity of the drug under the described test conditions and can be interpreted for clinical management purposes by considering other factors, such as drug pharmacology or antifungal resistance mechanisms.
Who is ISO 16256 for?
ISO 16256 is applicable to-
- Clinical laboratory conducting Vitro diagnostic test
- Research laboratories
- Healthcare facilities
Why should you use ISO 16256?
Dilution procedures are used to determine the minimum inhibitory concentrations (MICs) of antimicrobial agents and represent the reference method for antifungal susceptibility testing. MIC methods are used in resistance surveillance, comparative testing of new agents for research or registration purposes, to establish the susceptibility of organisms that give equivocal results in routine tests, for tests with organisms where routine tests can be unreliable, and when a quantitative result is needed for clinical management
The reference methods described in ISO 16256 are intended for the testing of pure cultures of yeast fungi. The laboratory that wishes to use ISO 16256 for conducting studies of newer antifungal agents, or as a reference method for comparison to MICs generated by a diagnostic device, can select which of the procedure options to use based upon the choice of MIC reading determined by visual inspection (CLSI method) or by use of a spectrophotometer (EUCAST method). In either case, the procedural details for that option should be followed explicitly.
What’s changed since the last update?
BS EN ISO 16256:2021 supersedes ISO 16256:2012, which has been withdrawn. BS EN ISO 16256:2021 has some significant technical changes with respect to ISO 16256:2012, these include:
- Addition of “broth micro-dilution” to the title
- Removal of 48 h reading for candida species by the visual reading method
- Removal of definitions for susceptibility and resistance that are beyond the scope of this test performance document
- Inclusion of considerations for antifungal testing of yeast species with micro-dilution trays “treated” by manufacturers of the trays prior to use in the tests
- Updating of viable count testing methods for visual and spectrophotometer test pathways