EN ISO 16256:2021 PDF

Overview

EN ISO 16256:2021 - Clinical laboratory testing and in vitro diagnostic test systems - specifies the broth micro-dilution reference method for determining the in vitro activity of antimicrobial (antifungal) agents against yeast fungi that cause infectious diseases. This European adoption of ISO 16256:2021 provides a standardized reference procedure to measure minimum inhibitory concentrations (MICs) for organisms such as Candida spp. and Cryptococcus neoformans. The standard does not cover dimorphic yeast forms (e.g., Blastomyces, Histoplasma) or filamentous fungi (moulds).

Key topics and technical requirements

• Test method: Broth micro-dilution using disposable micro-dilution trays; title includes “broth micro-dilution” to emphasize the procedure.
• Two reading pathways:
  • Visual determination of MICs (aligned with CLSI methods)
  • Spectrophotometric determination of MICs (aligned with EUCAST methods)
• Medium specification: Detailed guidance on RPMI-1640 formulation shown to give reproducible antifungal susceptibility results.
• Antifungal agents: Preparation of stock and working solutions; the 2021 edition adds newer agents (e.g., isavuconazole, rezafungin) to testing and QC ranges.
• Inoculum and incubation: Procedures for inoculum preparation, inoculation of trays, and incubation conditions for both reading pathways.
• Reading and interpretation: How to determine MICs; clinical interpretation and clinical breakpoints are outside the document’s scope - users should consult CLSI and EUCAST interpretive tables for breakpoints.
• Quality control (QC): QC strains and procedures to validate test performance and ensure reproducibility.
• Annexes and references: Informative annexes for RPMI-1640 composition, McFarland standards, and an updated bibliography relevant to antifungal susceptibility testing.

Applications and who uses it

• Clinical microbiology laboratories performing antifungal susceptibility testing for patient management and resistance surveillance.
• Regulatory and diagnostic developers validating or registering routine susceptibility tests and in vitro diagnostic devices against a recognized reference method.
• Research and pharmaceutical labs comparing new antifungal agents or conducting epidemiological studies of antifungal resistance.
• Public health and surveillance programs tracking MIC distributions to define wild-type vs non-wild-type populations.

Related standards and guidance

• CLSI and EUCAST method documents and interpretive breakpoint tables for clinical category assignment (susceptible, intermediate, resistant) - consult the latest tables from these organizations.
• ISO/TC 212 and CEN/TC 140 guidance on in vitro diagnostic test systems and standardization practices.

EN ISO 16256:2021 is essential for consistent, reproducible antifungal susceptibility testing by broth micro-dilution and supports harmonized laboratory practice across clinical, regulatory and research settings.