ISOTC 34SC 9 WG 4

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??????????? ISO/TC 34/SC 9 WG 4

• ISO Guide 43
• Microbiology of food and animal feeding stuffs
  Specific requirements and guidance for
  proficiency testing by interlaboratory comparison

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Background
ISO Guide 43Microbiology of food and animal
feeding stuffs (WD 22117) Specific
requirements and guidance for proficiency testing
by interlaboratory comparison

• Developed (initial work) under direct
  responsibility of
• ISO Technical Committee 34 (TC 34/SC 9)Food
  products Microbiology
• The further development of this standard was
  done by
• Working Group 4 Proficiency testing
• Mirror committeeTC 957 Microbiology of food
  and agricultural
• products
• Thai experts in WG4 Mrs.Pensri Rodma (DMS)
• Mrs. Nitaya Pirapatrungsuriya (NFI)
• Mr. Narit Lerkoung (TISI)

ISO/IEC 17025
ISO Guide 43 Part 1 2
(5.9 Assuring the quality of test and calibration
results)
WD 22117
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Participation
4th meetingHeld on 16th of January 2007, Paris,
France. Working draft of Specific requirements
for proficiency testing by interlaboratory
comparison
5th meetingHeld on 24th of April 2007, Cairo,
Egypt. Working draft of Specific requirements
and guidance for proficiency testing by
interlaboratory comparison
ISO CD 22117
6th meetingHeld in February, 2008 ISO/CD 22117
of Specific requirements and guidance for
proficiency testing by interlaboratory
comparison
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Objectives

• Evaluation of performance, particularly
  trueness (bias) and,
• in some cases, precision of food
  microbiological examinations
• in specific laboratories.

Data from PT can be used

• To provide information to the organizations
  responsible for
• laboratory acceptance within an official
  control framework and
• to allow continuous control
• To aid laboratory accreditation in a general
  framework of
• quality management
• To inform those responsible for quality in the
  participating
• laboratories as part of the educative elements
  of external
• quality assessment of trueness (bias).

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1. Scope

• Food
• Animal feeding stuffs
• Food production environment and food handling
• Primary production stage
• Water

This document is to be used in conjunction with
ISO/IEC Guide 43-1 and ISO 13528, and deals only
with areas where specific or additional details
are necessary for PT schemes for food
microbiology.
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2. Normative references
ISO 13528 Statistical methods for use in
proficiency testing by interlaboratory
comparisons ILAC Guide 13 ISO 7218 General
requirements and guidance for microbiological
examinations
3. Terms and definitions
Harmonize definitions with ISO 17043/ILAC Guide13
and WG 3 (Validation methods)
Disassociation of statistical and
microbiological terms

• Some terms used in the text have different
  meanings in
• microbiology and statistics, e.g.
• Homogeneity
• Heterogeneity
• Test
• Sample
• Distribution (e.g. d. of micro-organisms vs. d.
  of test results)

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4. Scheme design and purpose
4.1 Scheme objectives
The primary objective of any PT scheme is to
provide information to enable laboratories to
have confidence in the reliability of their
results
The studies required to establish new PT scheme
should include as a minimum the requirements
listed in section 5. Requirements for checking
individual rounds of testing, including
homogeneity and stability testing should also be
established in the scheme design and be
appropriate for the scheme objectives
4.2 Laboratory requirements for schemes
Criteria for selection for microbiology schemes
should include safety advice, for example, food
microbiology laboratories with facilities for
dealing with micro-organisms of Risk Categories
1, 2 and 3 as appropriate. (ISO 7218)
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4.3 Choice of test matrices
The reasons for the choice of matrix type must be
stated, for example, to provide levels of sample
stability and homogeneity that are fit for the
intended purpose of the scheme. The description
of the test items must specify the sample matrix.
4.4 Information on test methods used by the PT
provider
4.5 Statistical design
An outline of the statistical design for PT
schemes for microbiology should indicate that
the statistical tests to be used are influenced
by the level of homogeneity of the test
material. (Low numbers, Semi-quantitative
enumeration tests and qualitative detection )
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5. Technical requirements/guidance for sample
design and content
5.1 Target organisms level
The target organisms should be provided at levels
suitable to show that examination methods are
fit-for-purpose and to reflect levels likely to
be found in the sample matrices being tested.
Where pathogenic bacteria are the target, the
levels should also take account of and reflect
the levels causing hazard to human health.
5.2 Organisms sources, characterization and
traceability
5.3 Background/competitive flora
5.4 Matrix selection and effects
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6. Sample verification by the provider
6.1 Sample homogeneity testing general
considerations
A formal homogeneity test should be performed on
each batch of samples, based on relevant
statistical principles. (See ISO 13528, or as an
alternative, annex B) A test material which is
less than sufficiently homogenous, can still be
used in a proficiency test round, by making the
target standard deviation larger than usual, in
order to take account of the greater variance
between test portions (See ISO 13528).
6.2 Homogeneity testing for quantitative/enumerati
on samples
6.3 Homogeneity testing for qualitative methods
6.4 Stability testing by the provider

• Stability during storage conditions
• Stability during transport conditions

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7. Sample handling
7.1 Instructions to participants

• Storage conditions for samples of all types
• Maximum temperature of the samples on receipt at
  the
• participant laboratory, if appropriate
• Instructions on how to handle the samples
• Other supplementary instructions (e.g. the
  method(s) of
• examination and How to report the results to
  the organizers)

8. Performance evaluations
8.1 General introduction

• 8.2 Quantitative methods
• Distribution of data
• Determining the assigned value
• Uncertainty of the assigned value
• Uncertainty of the assigned value
• Methods of assessing performance
• Using z-scores
• Other methods of performance evaluation
• (e.g. Using the 0.5 log10 rule, percentiles,
  MPN)
• Long-term performance assessment

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• 8.3 Assessment of qualitative methods
• Performance of individual laboratories
• Scheme comparisons of laboratory performance
• Assessment of qualitative methods

Annex A (informative) Example of details to be
included in a PT scheme plan Annex B
(informative) Methods of testing for variation
between portions of Reference Materials
(RM) Annex C (informative) A practical method to
assess long-term performance of participants in
PT schemes using enumeration methods
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Resolutions from ISO/TC 34/SC 9 26th of meeting
1) SC 9 members asked the project leader (Sue
Passmore) to provide for November 2007 a
draft to be submitted to CD vote by the
secretariat. A WG 4 meeting should be
scheduled one month after the closure of
the CD vote to deal with the comments and to
prepare the draft for the DIS vote.
SC 9 members asked the project leader to come
with recommendations at the next SC 9
meeting for launching the DIS. 2) In order to
avoid any conflict with the revision of ISO guide
43-1 (future EN ISO 17043), SC 9 members
wished to establish a formal liaison with
CASCO and asked the secretariat to write a letter
to CASCO for a formal participation in WG 4
of one member of CASCO WG on EN ISO 17043.