EN ISO 17994:2004
(Main)Water quality - Criteria for establishing equivalence between microbiological methods (ISO 17994:2004)
Water quality - Criteria for establishing equivalence between microbiological methods (ISO 17994:2004)
ISO 17994:2004 defines an evaluation procedure for comparing two methods intended for the detection or quantification of the same target group or species of microorganisms.
ISO 17994:2004 provides the mathematical basis for the evaluation of the average relative performance of two methods against chosen criteria of equivalence.
Any two enumeration methods based on counts (of colonies or positive tubes) or any two detection methods (presence/absence methods) intended for the same purpose can be compared.
ISO 17994:2004 provides no solution to directly compare a quantitative method (colony count or MPN) with a detection method (P/A).
Wasserbeschaffenheit - Kriterien für die Feststellung der Gleichwertigkeit von mikrobiologischer Verfahren (ISO 17994:2004)
Diese Internationale Norm legt ein Bewertungsverfahren fest, um zwei Verfahren zu vergleichen, die für den Nachweis oder die Quantifizierung derselben Zielgruppe oder Spezies von Mikroorganismen gedacht sind.
Diese Internationale Norm liefert die mathematische Grundlage für die Bewertung der durchschnittlichen relativen Leistungsfähigkeit von zwei Verfahren unter Heranziehung festgelegter Gleichwertigkeitskriterien.
Zwei beliebige quantitative Nachweisverfahren, die auf Zählungen (von Kolonien oder positiven Röhrchen) beruhen oder zwei beliebige qualitative Nachweisverfahren (Anwesenheit-/Abwesenheit-Verfahren), die dieselbe Zielsetzung haben, können verglichen werden.
Diese Internationale Norm liefert keine Lösung, um ein quantitatives Verfahren (Koloniezählung oder MPN) direkt mit einem qualitativen Nachweisverfahren (P/A) zu vergleichen.
Qualité de l'eau - Critères pour établir l'équivalence entre les méthodes microbiologiques (ISO 17994:2004)
L'ISO 17994:2004 définit une procédure d'évaluation qui permet de comparer deux méthodes visant à détecter ou à quantifier le même groupe cible ou la même espèce de micro-organismes.
L'ISO 17994:2004 fournit les bases mathématiques pour évaluer les performances relatives moyennes des deux méthodes par rapport à des critères d'équivalence déterminés.
Deux méthodes quelconques de dénombrement fondées sur des comptages (de colonies ou de tubes positifs) ou deux méthodes quelconques de détection [méthodes présence/absence (P/A)] visant au même objectif peuvent être comparées.
L'ISO 17994:2004 n'indique aucune solution qui permette de comparer directement une méthode quantitative (comptage de colonies ou NPP) avec une méthode de détection (P/A).
Kakovost vode - Merila za ugotavljanje enakovrednosti mikrobioloških metod (ISO 17994:2004)
General Information
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Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Kakovost vode - Merila za ugotavljanje enakovrednosti mikrobioloških metod (ISO 17994:2004)Wasserbeschaffenheit - Kriterien für die Feststellung der Gleichwertigkeit von mikrobiologischer Verfahren (ISO 17994:2004)Qualité de l'eau - Criteres pour établir l'équivalence entre les méthodes microbiologiques (ISO 17994:2004)Water quality - Criteria for establishing equivalence between microbiological methods (ISO 17994:2004)07.100.20Mikrobiologija vodeMicrobiology of waterICS:Ta slovenski standard je istoveten z:EN ISO 17994:2004SIST EN ISO 17994:2004en,fr,de01-november-2004SIST EN ISO 17994:2004SLOVENSKI
STANDARD
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN ISO 17994May 2004ICS 07.100.20; 13.060.70English versionWater quality - Criteria for establishing equivalence betweenmicrobiological methods (ISO 17994:2004)Qualité de l'eau - Critères pour établir l'équivalence entreles méthodes microbiologiques (ISO 17994:2004)Wasserbeschaffenheit - Kriterien für die Feststellung derGleichwertigkeit von mikrobiologischen Verfahren (ISO17994:2004)This European Standard was approved by CEN on 9 April 2004.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Central Secretariat or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2004 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 17994:2004: ESIST EN ISO 17994:2004
Foreword
This document (EN ISO 17994:2004) has been prepared by Technical Committee ISO/TC 147 "Water quality" in collaboration with Technical Committee CEN/TC 230 "Water analysis", the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by November 2004, and conflicting national standards shall be withdrawn at the latest by November 2004.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
Endorsement notice
The text of ISO 17994:2004 has been approved by CEN as EN ISO 17994:2004 without any modifications.
Reference numberISO 17994:2004(E)© ISO 2004
INTERNATIONAL STANDARD ISO17994First edition2004-05-15Water quality — Criteria for establishing equivalence between microbiological methods Qualité de l'eau — Critères pour établir l'équivalence entre les méthodes microbiologiques
ISO 17994:2004(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this area. Adobe is a trademark of Adobe Systems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
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ISO 2004 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body in the country of the requester. ISO copyright office Case postale 56 • CH-1211 Geneva 20 Tel.
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ii © ISO 2004 – All rights reserved
ISO 17994:2004(E) © ISO 2004 – All rights reserved iii Contents Page Foreword.iv Introduction.v 1 Scope.1 2 Normative references.1 3 Terms, definitions and symbols.1 4 Principle.4 5 Basic requirements for an equivalence experiment.4 6 Calculations.8 7 Evaluation.10 8 Test report.12 Annex A (informative)
Flowchart.13 Annex B (informative)
Collaborative equivalence trials.14 Annex C (informative)
Example.16 Bibliography.18
ISO 17994:2004(E) iv © ISO 2004 – All rights reserved Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 17994 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 4, Microbiological methods. SIST EN ISO 17994:2004
ISO 17994:2004(E) © ISO 2004 – All rights reserved v Introduction This International Standard presents the criteria and procedures for assessing the average quantitative equivalence of the results obtained by two microbiological analytical methods one of which may but need not be a standard or reference method. The methods considered are based on counts of colonies or of positive and negative liquid enrichment tubes (MPN and presence/absence methods). NOTE It is possible that a method that is not quantitatively equivalent with a reference method would be accepted, especially if it appears “better” than the reference either quantitatively or otherwise.
INTERNATIONAL STANDARD ISO 17994:2004(E) © ISO 2004 – All rights reserved 1 Water quality — Criteria for establishing equivalence between microbiological methods WARNING — Persons using this International Standard should be familiar with normal laboratory practice. This International Standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions. 1 Scope This International Standard defines an evaluation procedure for comparing two methods intended for the detection or quantification of the same target group or species of microorganisms. This International Standard provides the mathematical basis for the evaluation of the average relative performance of two methods against chosen criteria of equivalence. Any two enumeration methods based on counts (of colonies or positive tubes) or any two detection methods [presence/absence (P/A) methods] intended for the same purpose can be compared. This International Standard provides no solution to directly compare a quantitative method (colony count or MPN) with a detection method (P/A). 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO/TR 13843:2000, Water quality — Guidance on validation of microbiological methods 3 Terms, definitions and symbols 3.1 Terms and definitions For purposes of this document, the following terms and definitions apply. 3.1.1 General terms 3.1.1.1 reference method prescribed analytical method to analyse a given group or species of microorganisms NOTE As a rule, the reference method is a standard or a commonly used method. 3.1.1.2 trial method any method which is to be tested for equivalence with a reference method SIST EN ISO 17994:2004
ISO 17994:2004(E) 2 © ISO 2004 – All rights reserved 3.1.1.3 equivalent method method considered quantitatively equivalent with another method when the average relative difference of their confirmed counts is found “not different” when following the calculations specified in this International Standard 3.1.1.4 standard uncertainty uncertainty of the result of a measurement expressed as a standard deviation [GUM] 3.1.1.5 expanded uncertainty quantity defining an interval about the result of a measurement that may be expected to encompass a large fraction of the distribution of values that could reasonably be attributed to the measurand NOTE The fraction may be viewed as the coverage probability or level of confidence of the interval. To associate a specific level of confidence requires explicit or implicit assumptions regarding the probability distribution. The level of confidence may be attributed to this interval only to the extent to which such assumptions may be justified. [GUM] 3.1.1.6 coverage factor numerical factor used as a multiplier of the (combined) standard uncertainty in order to obtain an expanded uncertainty NOTE The coverage factor, k = 2 is chosen for this International Standard because the distribution of the relative difference is unlikely to be normal; the expanded uncertainty corresponds only approximately to the 95 % confidence interval. 3.1.2 Specific terms 3.1.2.1 count observed number of objects, e.g. colonies or cells of microorganisms, plaques of bacteriophages NOTE In this International Standard, the result of an MPN estimation is also considered a count. 3.1.2.2 presumptive count number of objects that according to their outward appearance should presumably be included in the count 3.1.2.3 confirmed count count corrected for false positive results by further testing of the presumptive objects 3.1.2.4 relative difference RD difference between two results, a and b, measured on a relative (natural logarithmic) scale NOTE The value of RD, x, expressed in percent, is given by x = [ln(a) − ln(b)] × 100 % SIST EN ISO 17994:2004
ISO 17994:2004(E) © ISO 2004 – All rights reserved 3 Essentially the same result is given by 2()100%()abxab−=×+ until the ratio between a and b is greater than about 3. This accounts for the usage of the term “relative difference” in both cases. 3.2 Symbols and abbreviated terms A the (symbol for the idea of) trial method a a test result by Method A ai the test result (confirmed count) of Method A in sample i B the (symbol for the idea of) reference method b a test result by Method B bi the test result (confirmed count) of Method B in sample i C coefficient for computing the number of samples, given the value of the experimental variance
D maximum acceptable deviation (value of confidence limit) in the case Methods A and B are “not different” i running index k coverage factor used for calculating the expanded uncertainty L smallest significant (i.e. maximum acceptable) relative difference between Methods A and B MPN most probable number quantitative method m number of parallel tubes per dilution in an MPN series n number of samples nA number of samples where for the P/A Method, A is
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