ISO 19036:2019

Overview

ISO 19036:2019 - Microbiology of the food chain: Estimation of measurement uncertainty for quantitative determinations - provides requirements and guidance for estimating and expressing measurement uncertainty (MU) for quantitative microbiological results across the food chain. It covers analyses of foods, animal feed, environmental samples in food production/handling, and primary production samples. The standard focuses on enumeration methods (colony-count techniques) but is also applicable to MPN, instrumental (impediometry, ATP, flow cytometry) and molecular methods (qPCR). Note: the uncertainty estimated by ISO 19036:2019 does not include systematic effects (bias).

Key topics and requirements

• Top‑down (global) approach: Uses reproducibility-based estimates rather than full analytical input‑models when those are impractical for microbiological measurands.
• Three principal uncertainty components:
  • Technical uncertainty: Estimated from reproducibility (intralaboratory or interlaboratory) standard deviations; intralaboratory reproducibility design aligns with ISO 16140‑3.
  • Matrix uncertainty: Accounts for heterogeneity and distribution of microorganisms within the sample/matrix.
  • Distributional uncertainty: Statistical components such as Poisson uncertainty for colony counts, confirmation uncertainty for presumptive counts, and MPN intrinsic variability.
• Combination and expression: Guidance on combining standard uncertainties (ISO/IEC Guide 98‑3 “GUM” principles) into combined and expanded uncertainty values and how to report them in test reports, including results below the limit of quantification.
• Practical tools: Worked examples and informative annexes covering calculation methods, matrix effects, MPN variability, and correction of unwanted components.

Applications

ISO 19036:2019 helps laboratories and organizations:

• Produce defensible quantitative microbiology results with an expressed level of confidence.
• Support method validation, verification, and routine quality assurance for colony counts, MPN, qPCR and instrumental techniques.
• Improve reporting to clients and regulators by providing standardized MU information useful for compliance decisions, risk assessment, and trend analysis.
• Design intralaboratory experiments to estimate reproducibility and partition uncertainty components.

Who should use this standard

• Clinical and food‑testing laboratories
• Quality assurance/quality control managers in food industry
• Method developers and validation teams
• Accreditation bodies and regulatory authorities assessing laboratory performance

Related standards

• ISO/IEC Guide 98‑3 (GUM) - Measurement uncertainty principles
• ISO 16140‑3 - Verification of quantitative methods (related intralaboratory design)
• ISO 29201 - Water microbiology uncertainty approach (similar methodology)
• ISO/IEC 17025 - Laboratory competence and MU expectations

Keywords: ISO 19036:2019, measurement uncertainty, microbiology of the food chain, colony-count, MPN, qPCR, Poisson uncertainty, matrix uncertainty, technical uncertainty, lab reporting.