Overview
ISO 33406:2024 - Approaches for the production of reference materials with qualitative properties - provides practical guidance for implementing ISO 17034 when producing reference materials (RMs) or certified reference materials (CRMs) that have one or more qualitative (categorical) property values. The standard addresses how to assign qualitative values (primarily nominal properties), express uncertainty and confidence for non‑numerical results, and establish appropriate traceability for qualitative determinations. It supplements ISO 17034 and focuses on qualitative (not quantitative) property values.
Key topics and requirements
- Scope and definitions
- Clarifies terminology for qualitative properties (nominal and ordinal) and the focus on nominal properties.
- Characterization approaches
- Guidance on characterizing materials by provenance, identity based on measurements, or a combination of methods.
- Traceability for qualitative values
- Describes the role of a documented unbroken chain of qualitative comparisons and how reference data and reference materials support traceability for qualitative determinations.
- Uncertainty and confidence
- Explains expressing uncertainty for qualitative assignments as probabilities or confidence levels, and the interplay with quantitative measurements that underpin qualitative decisions.
- Statistical methods
- Recommendations for statistical approaches tailored to qualitative value assignment, including homogeneity and stability study designs.
- Homogeneity, stability and commutability
- Practical requirements and experimental designs for assessing homogeneity, stability and commutability of qualitative RMs.
- Sector examples and annexes
- Informative annexes include guidance for DNA and protein RMs, methods to express confidence, statistical procedures and worked examples.
Practical applications
- Supports production of RMs used in:
- Clinical diagnostics (e.g., identity/sequence RMs), molecular biology, food and environmental testing, forensics, and industrial quality control where qualitative decisions (species ID, presence/absence, genotype calls) are critical.
- Helps RM producers and laboratories:
- Design value‑assignment workflows for qualitative properties, document traceability chains, quantify and communicate confidence in categorical results, and plan homogeneity/stability studies.
- Useful for accreditation bodies, method developers, and regulatory laboratories requiring robust RMs for method validation and proficiency testing.
Related standards
- ISO 17034 (competence of RM producers) - primary normative baseline
- ISO 33401 (RM certificates and documentation)
- ISO Guide 30, ISO/IEC Guide 99 (VIM)
- Background references: ISO 33405, ISO Guide 80, ISO/TR 79
Keywords: ISO 33406:2024, reference materials, qualitative properties, ISO 17034, metrological traceability, measurement uncertainty, homogeneity, stability, commutability, CRMs.
