ISO INTERNATIONAL STANDARD 22117 First edition 2019-02 Microbiology of the food chain - Specific requirements and guidance for proficiency testing by interlaboratory comparison Microbiologiede la chaine alimentaire-Exigences spécifiques et recommandationsrelativesauxessaisd'aptitudeparcomparaison interlaboratoires Reference number IS0 22117:2019(E) Tso IS02019 IS0 22117:2019(E) COPYRIGHTPROTECTEDDOCUMENT @ ISO 2019 All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either IsO at the address below or Iso's member body in the country of the requester. ISO copyright office CP 401 : Ch. de Blandonnet 8 CH-1214 Vernier, Geneva Phone: +4122 749 0111 Fax: +41 22 749 09 47 Email: [email protected] Website: www.iso.org Published in Switzerland ii @ IS0 2019 - All rights reserved IS0 22117:2019(E) Contents Page Foreword ..V Introduction. ...vi 1 Scope. 2 Normative references ..1 3 Terms and definitions ..1 4 Scheme design and purpose .2 4.1 General .2 4.2 Scheme objectives.. .2 4.3 Laboratory requirements for schemes. 3 4.4 Choice of test matrices .3 4.5 Information on test methods used by the PT provider .3 4.6 Statistical design. .3 5 Technical requirements and guidance for sample design and content ..4 5.1 Sources, characterization and traceability of organisms 4 5.2 Target organisms level ..4 5.3 Non-target organisms and interferences .5 5.4 Matrix selection and effects ..5 6 Sample verification by the provider. ..6 6.1 General. .6 6.2 Sample homogeneity testing General considerations .6 6.3 Homogeneity testing for quantitative (enumeration) samples .6 6.4 Homogeneity testing for qualitative methods. .7 6.5 Stability testing by the provider. ..8 6.5.1 General ..8 6.5.2 Stability during storage conditions. 6.5.3 Stability during transport conditions ..8 7 Sample handling .9 7.1 General .9 7.2 Instructions to participants .9 8 Performance evaluations. .9 8.1 General. .9 8.2 Preliminary considerations... .9 8.3 Assessment of quantitative methods .10 8.3.1 General .10 8.3.2 Distribution of data. .11 8.3.3 Determining the assigned value .12 8.3.4 Uncertainty of the assigned value .12 8.3.5 Methods of assessing performance .12 8.3.6 Using z-scores .12 8.3.7 Other methods of performance evaluation .14 8.3.8 Long-term performance assessment. ..16 8.4 Assessment of qualitative methods. ..17 8.4.1 General ..17 8.4.2 Performance of individual laboratories .17 8.4.3 Scheme comparisons of laboratory performance .19 Annex A (informative) Example of details to be included in a PT scheme plan. ..21 Annex B (informative) Preparation of fungal spore suspensions. ..23 Annex C (informative) Methods of testing for variation between portions of test materials ..24 Annex D (informative) Example of a safety data sheet. .28 @ IS0 2019 - All rights reserved iii