Overview
EN ISO 20776-2:2022 (ISO 20776-2:2021) specifies how to evaluate the performance of antimicrobial susceptibility test (AST) devices that report minimum inhibitory concentrations (MICs) using a reference broth micro-dilution method. Developed by ISO/TC 212 in collaboration with CEN/TC 140, this standard defines acceptable performance criteria, test procedures, quality control and data-analysis approaches to guide manufacturers and laboratories in validating in vitro diagnostic (IVD) AST devices.
Key topics and technical requirements
- Reference method: Use of broth micro-dilution as the comparator for MIC determination and clear handling of inter-method variability.
- Strain selection: Requirements for representative strain panels including contemporary isolates and reference strains to ensure clinically relevant performance evaluation.
- Quality control (QC): QC practices for both the reference method and the AST device under evaluation, with cross-reference to authoritative QC ranges (e.g., EUCAST/CLSI guidance).
- Reproducibility testing: Protocols to assess repeatability and reproducibility of the AST device across runs, operators and sites.
- Isolate testing and inoculum preparation: Standardized procedures for preparing and testing isolates to reduce procedural bias.
- Discrepancy resolution: Defined processes for investigating and resolving MIC discrepancies between the device and reference method.
- Data analysis and acceptance criteria: Statistical approaches for assessing device accuracy, including bias analysis for MIC devices and sensitivity/specificity analyses for qualitative AST devices. Annexes provide rationale and worked guidance for MIC evaluation, bias analysis and sensitivity/specificity calculations.
Applications and intended users
- IVD manufacturers validating and gaining regulatory approval for automated or manual AST systems.
- Clinical microbiology laboratories implementing new AST devices and performing method verification.
- Regulatory and conformity assessment bodies reviewing performance evidence submitted for market authorization.
- Quality assurance and clinical validation teams designing performance evaluation studies and interpreting MIC agreement, reproducibility and QC outcomes.
Use cases include comparative device validation, lot-to-lot verification, multicenter clinical performance studies, and surveillance-focused MIC testing.
Related standards and resources
- Other parts of the ISO 20776 series (refer to ISO website for the full list).
- Referenced QC guidance from EUCAST and CLSI for quality control ranges and practices.
- Supersedes EN ISO 20776-2:2007; prepared under ISO/TC 212 and CEN/TC 140.
Keywords: antimicrobial susceptibility testing, AST devices, MIC, broth micro-dilution, in vitro diagnostics, EN ISO 20776-2:2022, performance evaluation, reproducibility, quality control, bias, sensitivity specificity.