1、BRITISH STANDARD BS EN ISO 17994:2004 BS 6068-4.19:2004 Water quality Criteria for establishing equivalence between microbiological methods The European Standard EN ISO 17994:2004 has the status of a British Standard ICS 07.100.20; 13.060.70 BS EN ISO 17994:2004 This British Standard was published u
2、nder the authority of the Standards Policy and Strategy Committee on 12 June 2004 BSI 12 June 2004 ISBN 0 580 43873 2 National foreword This British Standard is the official English language version of EN ISO 17994:2004. It is identical with ISO 17994:2004 The UK participation in its preparation was
3、 entrusted by Technical Committee EH/3, Water quality, to Subcommittee, EH/3/4, Microbiological methods, which has the responsibility to: A list of organizations represented on this subcommittee can be obtained on request to its secretary. Cross-references The British Standards which implement inter
4、national or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purp
5、ort to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committe
6、e any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN ISO title page, the EN ISO
7、foreword page, the ISO title page, pages ii to v, a blank page, pages 1 to 18, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEANSTANDARD NORMEEUROP
8、ENNE EUROPISCHENORM ENISO17994 May2004 ICS07.100.20;13.060.70 Englishversion WaterqualityCriteriaforestablishingequivalencebetween microbiologicalmethods(ISO17994:2004) QualitdeleauCritrespourtablirlquivalenceentre lesmthodesmicrobiologiques(ISO17994:2004) WasserbeschaffenheitKriterienfrdieFeststell
9、ungder GleichwertigkeitvonmikrobiologischenVerfahren(ISO 17994:2004) ThisEuropeanStandardwasapprovedbyCENon9April2004. CENmembersareboundtocomplywiththeCEN/CENELECInternalRegulationswhichstipulatetheconditionsforgivingthisEurope an Standardthestatusofanationalstandardwithoutanyalteration.Uptodatelis
10、tsandbibliographicalreferencesconcernings uchnational standardsmaybeobtainedonapplicationtotheCentralSecretariatortoanyCENmember. ThisEuropeanStandardexistsinthreeofficialversions(English,French,German).Aversioninanyotherlanguagemadebytra nslation undertheresponsibilityofaCENmemberintoitsownlanguage
11、andnotifiedtotheCentralSecretariathasthesamestatusast heofficial versions. CENmembersarethenationalstandardsbodiesofAustria,Belgium,Cyprus,CzechRepublic,Denmark,Estonia,Finland,France, Germany,Greece,Hungary,Iceland,Ireland,Italy,Latvia,Lithuania,Luxembourg,Malta,Netherlands,Norway,Poland,Portugal,
12、Slovakia, Slovenia,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROPEANCOMMITTEEFORSTANDARDIZATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2004CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwideforCENnationalMembers. Ref.No
13、.ENISO17994:2004:E I NESO 71:4992004 (E) 2 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 gi
14、ven 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 organiz
15、ations 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, Slov
16、enia, 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. ENISO17994:2004 Reference number ISO 17994:2004(E)INTERNATIONAL ADNATSDR ISO 14997 tide tsriFino -400251-50 Water quality Criter
17、ia for establishing equivalence between microbiological methods Qualit de leau Critres pour tablir lquivalence entre les mthodes microbiologiques Referecne unbmer OSI 49971002:)E(4INTERNATIONAL STANDARD ISO 17994 First edition 2004-05-15 uq retaWtilay atse rof airetirCbihsilgn iuqevateb ecnelween ib
18、orcimlolacigo temdohs Qlauuael ed ti rCrtise ruop tbaril uqlvilacnee ertne lse htmsedo cimrboloigoiuqse ENISO17994:2004IS:49971 O4002(E) DPlcsid Fremia ihTs PDF file mya ctnoian emdebt dedyfepcaes. In ccacnadrow eitA hebods licnesilop gnic,y tihs file mirp eb yatnde iv roweb detu slahl ton ide ebtln
19、u deess teh typfecaes wihce era hml era deddebicsnede ti dna onstlalde t noeh comuptfrep reromign tide ehtin.g In wodlnidaot gnihs fil,e trapise atpecc tiereht nser ehnopsiiblity fo nto ifnriigngn Aebods licnesilop gnic.y ehT ISO tneClar Secrteirata caceptl on siibality in this .aera Ai ebods a teda
20、rmfo kra Aebod SystemI snctaropro.de teDials fo teh sfotwcudorp erats sut deo crtaee tihs PDF file cna f ebi dnuon tlareneG eh Ifnler oatit evt oeh file; tP ehDc-Frtaeino marapterew stpo ereimizde fro irptni.gn Evyre cera neeb sah takne tsne oeru taht teh file is siutlbae fosu re yb ISO memdob rebei
21、s. In tlnu ehikletneve y ttah lborp aem lertait gno it is f,dnuo plsaee ifnrom ttneC ehlar Secterirata ta teh serddaig sleb nevwo. ii ENISO17994:2004ISO 17994:2004(E) iiiContents Page Foreword iv Introduction v 1 Scope 1 2 Normative references . 1 3 Terms, definitions and symbols 1 4 Principle . 4 5
22、 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 ENISO17994:2004ISO 17994:2004(E) iv Foreword ISO (t
23、he 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 commit
24、tee 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 electrotech
25、nical 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
26、 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
27、 any or all such patent rights. ISO 17994 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 4, Microbiological methods. ENISO17994:2004ISO 17994:2004(E) vIntroduction This International Standard presents the criteria and procedures for assessing the average quantitative
28、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 pos
29、sible 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. ENISO17994:2004ENISO17994:2004INTENRATIONAL TSANDADR IS:49971 O4002(E)1Water quality Criteria for establishing
30、 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
31、 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 mi
32、croorganisms. 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/ab
33、sence (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 appli
34、cation 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
35、 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 m
36、ethod. 3.1.1.2 trial method any method which is to be tested for equivalence with a reference method ENISO17994:2004ISO 17994:2004(E) 2 3.1.1.3 equivalent method method considered quantitatively equivalent with another method when the average relative difference of their confirmed counts is found “n
37、ot 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 b
38、e 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 as
39、sumptions 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 e
40、xpanded 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 obse
41、rved 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 inc
42、luded 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
43、, is given by x = ln(a) ln(b) 100 % ENISO17994:2004ISO 17994:2004(E) 3Essentially the same result is given by 2( ) 100 % () ab x ab = +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 ter
44、ms A the (symbol for the idea of) trial method a a test result by Method A a ithe 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 b ithe test result (confirmed count) of Method B in sample i C coefficient for computing
45、 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 accepta
46、ble) 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 n Anumber of samples where for the P/A Method, A is positive and B negative n Bnumber of samples where for the P/A Method, A is n
47、egative and B positive P/A presence/absence detection method s experimental standard deviation (standard uncertainty) s 2experimental variance x s standard deviation (standard uncertainty) of the mean U expanded uncertainty x relative difference x ivalue of the relative difference between a iand b i
48、in sample i x arithmetic mean of x i(i = 1,2,n) x Lvalue of the relative difference at the approximate lower 95 % confidence limit, derived by subtracting the value of the expanded uncertainty from the mean x Hvalue of the relative difference at the approximate upper 95 % confidence limit, derived by adding the value of the expanded uncertainty to the mean X 2experimental Poisson index of dispersion y conditional variable used in computing the number of samples for equivalence testing and/or verification ENIS
