Page 74 - 2013 ISPAM Mid-Year Mtg Book

All samples must be correctly identified.
4.2 Verification of Quantitative Methods
In order to verify laboratory performance, measure repeatability by analyzing 10 replicate
samples of a representative food matrix artificially inoculated at the same level at the
regulatory limit and within the quantification range of the method.
The selected food matrix may be inoculated with unstressed cells without any equilibration
period. The inoculum must be quantified using a direct plating method on non e-selective agar
to ascertain that the regulatory limit intent/expected inoculation level is reached.
The repeatability can be calculated according to sections 2.2.2 and 6.7 of G108 (reference
number).
It is possible to compare the reproducibility data to repeatability data from historic laboratory
data ………….. As a guide the repeatability (r) must be less than half of the reproducibility (R)
data presented in table 1 or published data. 2r < R. If R value if published.
Alternatively, prepare an inoculum, inoculate 10 food samples and quantify. Simultaneously
plate the inoculum on 10 agars, quantify and calculated the mean and standard deviation and
used it as your cvr.
This will probably work with method without resuscitation step before enumeration.
Question around if this could work with MPN methods.
Bioballs
For the verification of quantitative method, the use of certified reference material is
recommended, if available. Numerous suppliers offer this type of product.
5. References
6.1 ISO 16140:2003(E) Microbiology of food and animal feeding stuffs - Protocol for the validation of
alternative methods.
6.2 ISO 17025:2005 General requirements for the competence of testing and calibration laboratories
6.3CAN-P-1587 Requirements for the accreditation of agriculture inputs, food, animal health and
plant protection testing laboratories, April 2008
6.4 CAN-P-1629 PALCAN Guidance for the validation of test methods, November 2006 – under
revision and written specifically to address validation, not verification
6.5 CAN-P-1630 PALCAN Interpretations for conducting assessments of testing and calibration
laboratories, January 2008
6.6 You might add the AOAC Guide (ALACC Guide 2) for “How to meet the ISO 17025 Requirements
for Method Verification (2007), as it includes a section on micro but I disagree with what Michael
Brodsky says about “Verification of microbiological methods also requires that the following
parameters are addressed:
1. Laboratory competency of achieving method performance characteristics on an on-going basis.
2. Analyst performance: Can your analysts perform the method with the equivalent degree of
precision and accuracy?
We are talking about a process in which the analyst is integral. You could add requirements about
properly maintained and calibrated equipment too.
Comment [ii12]: THIS SECTION NEED
MORE WORK- TO BE WORKED ON IN MID
JANUARY MEETING
Comment [ii13]: According to the propose ISO
N130- 4 parameter should be evaluated for
quantitative method: trueness, repeatability,
reproducibility and MU- our approach do not include
all of them
ACTION: should we add a note saying that
because different than table
Comment [ii14]: ?????Do we need to define this
Comment [L15]: Insert sample equations for
calculations; leave flexibility to use those of other
similar docs/orgs. “The following equations are an
example of one way to calculate XYZ”? ACTION:
DANIEL TO INSERT EXEMPLE
Comment [L16]: Sam: Participation in PT panels
– where could this information be used in
verification? ACTION : II TO FOLLOW UP
WITH SAM
Comment [ii17]: ????vSize of the inoculum to
discuss
Comment [ii18]: This will be tested in the
Longueuil lab- ACTION Daniel will report at next
meeting
Comment [ii19]: ACTION: TG TO THINKS OF
WAY TO EVALUATE THIS.