ISO 17994-2014 PDF

Full title and description

ISO 17994:2014 — Water quality — Requirements for the comparison of the relative recovery of microorganisms by two quantitative methods. This International Standard specifies an evaluation procedure and the mathematical basis for comparing the average relative recovery (performance) of two quantitative microbiological methods intended to enumerate the same target group or species of microorganisms.

Abstract

ISO 17994:2014 provides a statistical evaluation procedure for method-comparison studies that assess the relative recovery of microorganisms by two quantitative methods. It explains how to calculate and interpret average relative differences, confidence limits and sample size considerations for method comparison, and clarifies that it does not itself provide precision data nor is it intended for single-laboratory verification of method performance.

General information

• Status: Published.
• Publication date: February 2014 (Edition 2, published 06 February 2014 / 2014-02).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 07.100.20 (Microbiology of water); 13.060.70 (Examination of biological properties of water).
• Edition / version: Edition 2 (2014), replaces ISO 17994:2004.
• Number of pages: 22 pages (official ISO edition).

Scope

This standard specifies an evaluation procedure for comparing two quantitative microbiological methods with established performance characteristics (as described in ISO/TR 13843). It is intended for the quantification of the same target group or species of microorganisms and provides the mathematical framework to evaluate the average relative performance between the two methods, including decision criteria and sample-size guidance. The document does not provide precision estimates for the methods under test and is not a protocol for single-laboratory verification of method performance.

Key topics and requirements

• Statistical framework for comparing relative recovery between two quantitative methods (average relative differences and confidence intervals).
• Guidance on selection of comparison criteria and limits for microbiological equivalence.
• Sample size estimation and formulas for determining additional samples when initial results are inconclusive.
• Instructions for counting, confirmation and recording results in method-comparison studies.
• References to normative documents for method validation and enumeration (e.g., ISO/TR 13843 and ISO 8199).

Typical use and users

Used by microbiology laboratories, water-quality analysts, method developers, validation teams and regulatory bodies to assess whether a candidate or alternative quantitative microbiological method gives comparable recoveries to an established reference method. Typical applications include method evaluation during method development, inter-method validation for water testing (drinking, recreational, environmental) and regulatory submissions where method comparability must be demonstrated.

Related standards

Normative and related documents commonly referenced alongside ISO 17994:2014 include ISO/TR 13843 (Guidance on validation of microbiological methods) and ISO 8199 (General guidance on the enumeration of micro‑organisms by culture). The 2014 edition replaces ISO 17994:2004. National adoptions or identical transpositions may appear as EN ISO 17994:2014 in some regions.

Keywords

water quality, microbiology, method comparison, relative recovery, quantitative methods, method validation, ISO 17994, statistical evaluation, sample size, enumeration

FAQ

Q: What is this standard?

A: ISO 17994:2014 is an international standard that defines a statistical evaluation procedure for comparing the relative recovery (average relative performance) of microorganisms obtained by two quantitative microbiological methods.

Q: What does it cover?

A: It provides the mathematical basis, decision criteria and sample-size guidance to assess whether two methods yield comparable quantitative results for the same target microorganisms; it does not provide precision data for methods nor is it intended for single-laboratory verification.

Q: Who typically uses it?

A: Microbiology and water-quality laboratories, method developers, validation/QA teams, and regulatory agencies involved in assessing, validating or approving quantitative microbiological methods for water testing.

Q: Is it current or superseded?

A: The 2014 edition (Edition 2) is the current ISO edition published in February 2014 and replaces ISO 17994:2004. The standard is subject to periodic review (confirmation activity noted in 2019). Users should check their national adoption or the ISO catalogue for any amendments or later revisions.

Q: Is it part of a series?

A: ISO 17994 is part of the broader set of ISO guidance and standards on microbiological methods and method validation (for example ISO/TR 13843 and ISO 8199), and is aligned with the technical work of ISO/TC 147/SC 4 (microbiological methods for water).

Q: What are the key keywords?

A: Relative recovery, method comparison, water microbiology, quantitative methods, method validation, statistical evaluation, sample size.