1、DRAFT FOR DEVELOPMENT DD ENV ISO/TR 13843:2001 Incorporating Corrigendum No. 1. Water quality Guidance on validation of microbiological methods ICS 07.100.20 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWDD ENV ISO/TR 13843:2001 This Draft for Development, having been prepare
2、d under the direction of the Health and Environment Sector Committee, was published under the authority of the Standards Committee and comes into effect on 15 July 2001 BSI 11 October 2001 ISBN 0 580 37552 8 National foreword This Draft for Development is the official English language version of ENV
3、 ISO/TR 13843:2001. This publication is not to be regarded as a British Standard. It is being issued in the Draft for Development series of publications and is of a provisional nature as this is a rapidly changing field in which the technical aspects are still being developed. It should be applied o
4、n this provisional basis, so that information and experience of its practical application may be obtained. Comments arising from the use of this Draft for Development are requested so that UK experience can be reported to the European organization responsible for its conversion into a European Stand
5、ard. A review of this publication will be initiated 2 years after its publication by the European organization so that a decision can be taken on its status at the end of its three-year life. The commencement of the review period will be notified by an announcement in Update Standards. According to
6、the replies received by the end of the review period, the responsible BSI Committee will decide whether to support the conversion into a European Standard, to extend the life of the prestandard or to withdraw it. Comments should be sent in writing to the Secretary of BSI Subcommittee EH/3/4, Microbi
7、ological methods, at 389 Chiswick High Road, London W4 4AL, giving the document reference and clause number and proposing, where possible, an appropriate revision of the text. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The Brit
8、ish Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. Summary
9、of pages This document comprises a front cover, an inside front cover, the ENV ISO title page, the ENV ISO foreword page, the ISO/TR title page, pages ii to iv, pages 1 to 47 and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments i
10、ssued since publication Amd. No. Date Comments 13488 11 October 2001 Correction to ENV ISO title page and foreword.EUROPEANPRESTANDARD PRNORMEEUROPENNE EUROPISCHEVORNORM ENVISO13843 May2001 ICS07.100.20 Englishversion WaterqualityGuidanceonvalidationofmicrobiological methods(ISO/TR13843:2000) Qualit
11、deleauLignesdirectricespourlavalidationdes mthodesmicrobiologiques(ISO/TR13843:2000) WasserbeschaffenheitRichtliniezurValidierung mikrobiologischerVerfahren(ISO/TR13843:2000) ThisEuropeanPrestandard(ENV)wasapprovedbyCENon7April2001asaprospectivestandardforprovisionalapplication. Theperiodofvalidityo
12、fthisENVislimitedinitiallytothreeyears.AftertwoyearsthemembersofCENwillberequestedto submittheir comments,particularlyonthequestionwhethertheENVcanbeconvertedintoaEuropeanStandard. CENmembersarerequiredtoannouncetheexistenceofthisENVinthesamewayasforanENandtomaketheENVavailablepromp tly atnationalle
13、velinanappropriateform.Itispermissibletokeepconflictingnationalstandardsinforce(inparalleltothe ENV)untilthefinal decisionaboutthepossibleconversionoftheENVintoanENisreached. CENmembersarethenationalstandardsbodiesofAustria,Belgium,CzechRepublic,Denmark,Finland,France,Germany,Greece, Iceland,Ireland
14、,Italy,Luxembourg,Netherlands,Norway,Portugal,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROPEANCOMMITTEEFORSTANDARDIZATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2001CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwidefo
15、rCENnationalMembers. Ref.No.ENVISO13843:2001EgaPe2 VNEOSI8312:34001 CORRECTED20010815 Foreword ThetextoftheTechnicalReportfromTechnicalCommitteeISO/TC147“Waterquality“ofthe InternationalOrganizationforStandardization(ISO)hasbeentakenoverasaEuropean PrestandardbyTechnicalCommitteeCEN/TC230“Wateranaly
16、sis“,thesecretariatofwhich isheldbyDIN. ThisEuropeanPrestandardshallbegiventhestatusofanationalstandard,eitherby publicationofanidenticaltextorbyendorsement,atthelatestbyNovember2001,and conflictingnationalstandardsshallbewithdrawnatthelatestbyNovember2001. AccordingtotheCEN/CENELECInternalRegulatio
17、ns,thenationalstandardsorganizationsof thefollowingcountriesareboundtoannouncethisEuropeanPrestandard:Austria,Belgium, CzechRepublic,Denmark,Finland,France,Germany,Greece,Iceland,Ireland,Italy, Luxembourg,Netherlands,Norway,Portugal,Spain,Sweden,SwitzerlandandtheUnited Kingdom. Endorsementnotice The
18、textoftheTechnicalReportISO/TR13843:2000hasbeenapprovedbyCENasa EuropeanPrestandardwithoutanymodifications. ENVISO13843:2001Reference number ISO/TR 13843:2000(E) OSI 0002 TECHNICAL REPORT ISO/TR 13843 First edition 2000-06-01 Water quality Guidance on validation of microbiological methods Qualit de
19、leau Lignes directrices pour la validation des mthodes microbiologiques ENVISO13843:2001IS/OTR:34831(0002)E ii ENVISO13843:2001ISO/TR34831:0002()E iii Contents Page Foreword.iv 1 Scope 1 2 Terms and definitions .1 3 Arrangement of the document .8 4 Basic concepts.8 4.1 General8 4.2 Validation8 4.3 D
20、etectors 11 4.4 Performance characteristics 11 4.5 Specifications.11 5 Limitations and characteristic features of microbiological methods 12 5.1 Recovery of the analyte 12 5.2 Sample variance.12 5.3 Particle distribution and overdispersion.12 5.4 Interactions in the detector.12 5.5 Robustness 13 5.6
21、 Spurious errors13 5.7 Control and guidance charts13 6 Mathematical models of variation14 6.1 Unavoidable basic variation The Poisson distribution .14 6.2 Overdispersion The negative binomial model .17 6.3 Statistical and practical limits 20 6.4 General tests for randomness Detection of overdispersi
22、on 21 7 Specifications Current practice.21 8 Specifications Recommended approach22 9 Determination and expression of performance characteristics .23 9.1 General23 9.2 Categorical characteristics related to specificity and selectivity.23 9.3 Working limits 24 9.4 Working range of MPN procedures25 9.5
23、 Precision.25 10 Procedures and steps of validation.26 10.1 General26 10.2 Primary validation26 10.3 Secondary validation.28 11 Designs for determining specifications 28 11.1 A general model for basic quantitative specifications 28 11.2 Precision of the entire analytical procedure.29 11.3 Categorica
24、l characteristics.29 11.4 Unplanned data29 Annex A Statistical procedures and computer programs30 Annex B Numerical examples .34 Annex C Example of a validation experiment45 Bibliography46 ENVISO13843:2001IS/OTR :34831(0002)E iv Foreword ISO (the International Organization for Standardization) is a
25、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
26、 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 draft
27、ed in accordance with the rules given in the ISO/IEC Directives, Part 3. 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 Stan
28、dard requires approval by at least 75 % of the member bodies casting a vote. In exceptional circumstances, when a technical committee has collected data of a different kind from that which is normally published as an International Standard (“state of the art“, for example), it may decide by a simple
29、 majority vote of its participating members to publish a Technical Report. A Technical Report is entirely informative in nature and does not have to be reviewed until the data it provides are considered to be no longer valid or useful. Attention is drawn to the possibility that some of the elements
30、of this Technical Report may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO/TR 13843 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 4, Microbiological methods. ENVISO13843:2001TECINHCAL ROPETR IS/O
31、TR :34831(0002)E 1 Water quality Guidance on validation of microbiological methods 1 Scope This Technical Report deals with validation of microbiological methods, with particular emphasis on selective quantitative methods in which the quantitative estimate is based on counting of particles either di
32、rectly, with the aid of a microscope, or indirectly, on the basis of growth (multiplication) into colonies or turbidity. The principles and procedures within this scope are commonly known as the presence/absence (P/A), most probable number (MPN), colony count and direct (microscopic) count. This Tec
33、hnical Report does not apply to the validation of the so-called rapid or modern methods which mostly depend on measuring products or changes due to microbial activity but do not address the detection of individual particles. 2 Terms and definitions For the purposes of this Technical Report, the foll
34、owing terms and definitions apply. 2.1 accuracy of measurement closeness of the agreement between a test result and the accepted reference value NOTE The term “accuracy”, when applied to a set of test results, involves a combination of random components and a common systematic error or bias componen
35、t. ISO 3534-1:1993, 3.11 2.2 analyte measurand particular quantity subjected to measurement NOTE 1 See reference 5. NOTE 2 In microbiology the analyte is ideally defined as a list of taxonomically defined species. In many cases, in practice the analyte can only be defined by group designations less
36、accurate than taxonomic definitions. 2.3 analytical portion test portion volume of particle suspension inoculated into a detector unit NOTE Examples of a detector unit are agar plate, membrane filter, test tube, microscopic grid square. 2.4 application range range of particle concentrations routinel
37、y subjected to measurement by a method ENVISO13843:2001IS/OTR :34831(0002)E 2 2.5 categorical characteristic method performance characteristic numerically expressed as a relative frequency based on P/A or +/ classification 2.6 CFU, deprecated colony-forming unit, deprecated CFP, deprecated colony-fo
38、rming particle, deprecated NOTE The term was originally introduced to convey the idea that a colony may originate not only from a single cell but from a solid chain or aggregate of cells, a cluster of spores, a piece of mycelium, etc. It mistakenly equates the number of colonies observed to the numb
39、er of living entities seeded on the medium. Growth unit, viable particle, propagule (2.27) and germ (2.13) are terms with similar meanings but convey the original idea better and apply not only to colony-count methods but also to MPN and P/A. 2.7 coefficient of variation CV relative standard deviati
40、on for a non-negative characteristic, the ratio of the standard deviation to the average NOTE 1 The ratio may be expressed as a percentage. NOTE 2 The term “relative standard deviation“ is sometimes used as an alternative to “coefficient of variation“, but this use is not recommended. ISO 3534-1:199
41、3, 2.35 NOTE 3 In this Technical Report the term coefficient of variation (CV) is used when the relative standard deviation is expressed in percent (CV % = 100 RSD). 2.8 collaborative test method or laboratory performance test where several laboratories join in an experiment planned and co-ordinated
42、 by a leader laboratory NOTE Collaborative tests are mainly of two types. Intercalibration exercises are made to allow laboratories to compare their analytical results with those of other participating laboratories. Method performance tests produce precision estimates (repeatability, reproducibility
43、) out of data accumulated when several participating laboratories study identical samples with a strictly standardized method. 2.9 confirmed verified colony count x presumptive colony count corrected for false positives k x=pc= c n where c is the presumptive count; p is the true positive rate; n is
44、the number of presumptive positives isolated for confirmation; k is the number confirmed. ENVISO13843:2001IS/OTR :34831(0002)E 3 2.10 control chart two-dimensional scattergram for monitoring method performance with control values obtained by a Type A study NOTE In control charts the horizontal axis
45、is usually in the time scale or ordinate scale and the control variable is the mean or some precision measure (s, CV, RSD). 2.11 detector particle detector plate of solid matrix or a tube of liquid containing a nutrient medium for counting or detecting living microbial particles 2.12 detection set d
46、etector set combination of plates or tubes on which quantitative estimation of microbial concentration in a sample is based NOTE The detection set is the set of plates or tubes utilized for numerical estimation of a single value. EXAMPLES Parallel plates of a suspension, plates from consecutive dilu
47、tions, 3 5 tube MPN system, microtitre plate. 2.13 germ living entity capable of producing growth in a nutrient medium cf. propagule (2.27) 2.14 guidance chart two-dimensional scattergram for presenting method performance data (quantity or precision) with arbitrary guide values or guide values obtai
48、ned by Type B reasoning NOTE In guidance charts, the horizontal axis is usually the colony count per detector. 2.15 heterogeneous Poisson distribution distribution arising when the mean of a Poisson distribution varies randomly from occasion to occasion NOTE 1 See reference 11. NOTE 2 See also negative binomial distribution (2.19). 2.16 limit of detection particle number x (per analytical portion) where the probability p 0 of a negative result equals 5 % NOTE 1 Pr
