RB/T 033-2020 English PDF (RBT033-2020)

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RB/T 033-2020: Guidance on verification and validation of microbiological testing methods
RB/T 033-2020
RB
CERTIFICATION AND ACCREDITATION INDUSTRY
STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA
ICS 03.120.00
A 00
Guidance on verification and validation of microbiological
testing methods
ISSUED ON: AUGUST 26, 2020
IMPLEMENTED ON: DECEMBER 01, 2020
Issued by: Certification and Accreditation Administration
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 4
4 Method validation ... 8
4.1 General ... 8
4.2 Selection of characteristic parameters... 9
4.3 Validation method ... 9
4.4 Validation of characteristic parameters ... 11
5 Method verification ... 17
5.1 General ... 17
5.2 Selection of characteristic parameters... 17
5.3 Qualitative method ... 18
5.4 Quantitative method ... 18
Annex A (informative) Acceptability parameters and limits for paired and unpaired
studies in qualitative method validation ... 20
Annex B (informative) Estimating LOD50 based on the number of positive results per
contamination level ... 22
Bibliography ... 23
Guidance on verification and validation of microbiological
testing methods
1 Scope
This Standard provides laboratory guidance for method verification and validation of
microbiological testing methods.
This Standard applies to method verification of methods developed by laboratories,
standard methods used beyond their intended scope, and expanded and modified
standard methods. It is also suitable for method validation before the official use of
newly introduced standard methods in laboratories.
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 16140-2, Microbiology of the food chain-method validation - Part 2: Protocol
for the validation of alternative (proprietary) methods against a reference method
ISO/IEC 17025:2017, General requirements for the competence of testing and
calibration laboratories
ISO/IEC Guide 99: 2007, International vocabulary of metrology - Basic and general
concepts and associate terms (VIM)
3 Terms and definitions
For the purposes of this document, the terms and definitions defined in ISO/IEC Guide
99:2007 and ISO/IEC 17025:2017 as well as the followings apply.
3.1 method verification
Through verification or testing, the laboratory provides objective evidence to prove that
the requirements specified in the testing method are met. That is to provide objective
evidence to prove that the laboratory can correctly apply the method and ensure that the
required method performance is achieved.
NOTE 1: Where applicable, measurement uncertainty shall be considered.
NOTE 2: It is adapted from ISO/IEC Guide 99:2007, Definition 2.44.
3.2 method validation
Through testing, the laboratory provides objective evidence that the method to be
determined meets the intended use.
NOTE 1: Method validation shall identify the factors that affect method performance and their
degree of influence, verify the performance characteristics of the method, and determine the matrix
to which the method is applicable and the limitations of its use.
NOTE 2: Validation may include validation of sampling, handling and transportation procedures
for test items.
NOTE 3: It is adapted from ISO/IEC Guide 99:2007, Definition 2.45.
3.3 reference method
Methods that are recognized and widely accepted by international, national, industry or
organizations.
NOTE: The reference method gives priority to the methods recommended by the International
Organization for Standardization (ISO), Chinese National Standards (GB), and the Association of
Analysts International (AOAC). Other industry accepted methods may also serve as reference
methods.
3.4 qualitative method
An analytical method that detects the presence of target microorganisms using direct or
indirect methods.
3.5 quantitative method
An analytical method that measures the number of target microorganisms directly (such
as counting a certain mass or volume of samples) or indirectly (such as absorbance
value, impedance, etc.) on a certain number of samples.
3.6 confirmatory method
A method that can provide all or part of the information on the target, based on which
information can be clearly identified and, if necessary, quantified at the concentration
level of concern.
3.7 screening method
A method that has the ability to efficiently process large numbers of samples and is used
to detect the presence of a substance or group of substances at a concentration level of
interest.
NOTE: These methods are used to screen large numbers of samples for possible positive results
and to avoid false negative results. The detection results obtained by such methods are usually
qualitative results or semi-quantitative results.
3.8 sensitivity
The ability of a reference method or method to be validated to detect an analyte.
3.9 relative trueness; RT
The same sample is tested using the validation method and the reference method to see
how consistent the results are. That is, the sum of the number of validated positives and
the number of negative validated by both the method to be validated and the reference
method is divided by the total number of samples used for validation.
3.10 level of detection; LODx
Using a microbial qualitative detection method, through a given detection step, the
content of the measured analyte is obtained with a probability x of a positive detection
result.
Example: LOD50 means the level of detection at which 50% of tests give positive results.
[ISO 16140-1:2016, Definition 2.35]
3.11 relative level of detection; RLOD
For the same sample, the ratio of the level of detection (LODx) of the validated method
and the reference method.
3.12 estimated LOD50
LOD50 (positive result detection probability of 50%) is determined based on the
experimental design described in this Standard.
NOTE: Due to the very small number of test samples, the LOD50 cannot be determined accurately.
Therefore, the term estimated LOD50 is used.
3.13 inclusivity study
Research on qualitative or quantitative detection of purified target bacteria using
methods to be validated.
[ISO 16140-1:2016, Definition 2.31]
3.14 exclusivity study
Research on purified non-target bacteria using a method to be validated. These non-
target strains may be cross-reactive, but will ultimately not be qualified or quantified
difference between a specified value of a quantitative result and the mean of repeated
measurements.
[ISO 16140-1:2016, Definition 2.9]
3.20 estimated bias
Bias determined based on the experimental design described in this Standard.
NOTE: Due to the very small number of samples tested, bias cannot be accurately determined.
Therefore, the term estimated bias is used.
3.21 precision
Measurement precision. The degree of consistency between the indicated values or
measured quantities obtained by repeated measurements of the same or similar
measured objects under specified conditions.
NOTE 1: Measurement precision is usually expressed in terms of standard deviation, variance or
coefficient of variation under specified measurement conditions.
NOTE 2: "Specified conditions" may be, for example, repeatability measurement conditions,
intermediate precision conditions or reproducib...