Abstract

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.

SIST EN ISO 20776-2:2022 PDF

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Abstract

Overview

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Applications and intended users

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