Food Protection Trends - May/June 2023 - 275

GENERAL INTEREST PAPER
Evaluating Microbiological Method Equivalence -
A Decision Guide
J. David Legan,1* Laurie Post,2
Christina Barnes,3
Amanda Brookhouser-Sisney,4
Corrigan,6 Kristen A. Hunt,2 Ryan D. Maus,2 Sophie Pierre,7 Patricia Rule,8
1Eurofins Microbiology, 6304 Ronald Reagan Ave., Madison, WI 53704, USA
2Deibel Laboratories Inc., 7120 N. Ridgeway Ave., Lincolnwood, IL 60712, USA
32410 Conway Ave., 3M Building 260-06-B01, St. Paul, MN 55144-1000, USA
Midwest Laboratories, 13611 B St., Omaha, NE 68144, USA
5Diamond V, 2525 60th Ave. SW, Cedar Rapids, IA 52404, USA
6Hygiena, 941 Avenida Acaso, Camarillo, CA 93012, USA
4
7
8
Bio-Rad, 3 Boulevard Raymond Poincaré, 92430 Marnes-la-Coquette, France
bioMérieux, Inc., 595 Anglum Road, Hazelwood, MO 63042, USA
SUMMARY
Using an appropriate method is a key step in generating
reliable results; and, when those results are to be used to
make safety-critical decisions, method selection becomes
even more important. For microbiological testing, there
are national and international standard methods and
various other widely accepted methods. Performance of
such methods has usually been validated through some
kind of collaborative process or independent review.
An independent review may have resulted in some kind
of certification. Method validation, with or without
independent certification, demonstrates that a method has
performance equivalent to an established reference method.
Many circumstances can arise that cause a laboratory to
change methods. In such an event, how is a laboratory to
determine that two methods are equivalent to one another
if neither of them is a reference method? In this paper we
outline a thought process to guide this decision. The process
involves comparing existing validation and/or certification
data to determine whether two or more methods have been
compared against the same reference method for the matrices
of interest using a rigorous experimental and statistical
approach. If they have, the methods may be considered
equivalent, and a laboratory simply needs to verify its ability
to perform them. If they have not, then a formal validation
may be needed.
OVERVIEW
In previous articles by the International Association for
Food Protection Interest Group on Verification and Validation,
the increasing need for the most prudent, scientifically
and economically sound approaches to method validation
and verification was discussed (5). Suggestions for practical,
risk-based approaches to address this need focused on matrix
grouping and levels of test method evaluation in a second
publication (6). Following on this theme, this current article
discusses another approach that would alleviate verification
and validation testing pressure and reduce the burden of evaluation,
particularly when one is faced with choosing between
two or more validated methods. The most direct comparison
is when the methods are validated for the same target analyte
in the same validated matrix. When can we consider these
methods equivalent to one another without a direct comparison
between them? How does the reference method affect
this consideration? What if the validations do not include
exactly the same matrices? What other factors would play
into method selection? These questions and more are the
subject of frequent decisions in microbiology laboratories
around the world.
Before addressing these questions, it is helpful to have a
basic understanding of the process of method validation.
The starting point for validation of a new method is the
existing reference method against which the new method
is compared. There are minor differences in the definition
of reference among sources (1, 8, 15), but all are from
recognized sources such as the U.S. Food and Drug
Administration (FDA) Bacteriological Analytical Manual
(BAM), the U.S. Department of Agriculture (USDA)
Microbiology Laboratory Guidebook (MLG), the Health
Canada Compendium of Analytical Methods, standards from
the International Organization for Standardization (ISO),
and national standards from countries throughout the world.
Traditionally all are cultural methods.
The developer of a new qualitative method evaluates several
performance parameters including inclusivity, exclusivity,
robustness, and stability and the ability to detect the target
in a range of matrices following guides to validation such
as AOAC Appendix J (1) or ISO 16140-2 (9). There are
W. Evan Chaney,5
Nikki Taylor,8
Nisha
and Julie Weller6
*
Author for correspondence. Phone: +1 608.347.8486; Email: David.Legan@ft.eurofinsUS.com
May/June Food Protection Trends 275
https://www.foodprotection.org/files/food-protection-trends/may-jun-23-Legan.pdf
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