218 / 596
4
Receipt Confirmation form provided and fax or email it back to the study director.The shipment
1
and hold timesof the inoculated test material had been verified as a quality control measure prior
2
to study initiation.
3
4
Test Portion Analysis
5
6
Collaborators were instructed to follow the appropriate preparation and analysis as outlined in
7
the study protocol for each matrix for both the 3M MDA 2 -
Listeria monocytogenes
method and
8
reference method. For both matrices, each collaborator received 72 test portions (12 high, 12 low
9
and 12 un-inoculated controls for each method to be performed). For the analysis of the deli
10
turkey test portions by the 3M MDA 2 -
Listeria monocytogenes
method, a 125 g portion was
11
enriched with 975 mL of Demi-Fraser (DF) with ferric ammonium citrate (FAC) broth,
12
homogenized for 2 minutes and incubated for 24-28 hours at 37 ±1
o
C. For the raw chicken
13
breast fillettest portions analyzed by the 3M MDA 2 -
Listeria monocytogenes
method, a 25 g
14
portion was enriched with 475 mL of DF, homogenized for 2 minutes and incubated for 28-32
15
hours at 37 ±1
o
C.
16
Following enrichment, samples were assayed by the 3M MDA 2 -
Listeria monocytogenes
17
method and, regardless of presumptive result, confirmed following the USDA/FSIS MLG 8.09
18
reference method. Both matrices evaluated by the 3M MDA 2 -
Listeria monocytogenes
method
19
were compared to samples analyzed using the USDA/FSIS MLG 8.09 reference method in an
20
unpaired study design. All positive test portions were biochemically confirmed by the API
21
Listeria monocytogenes
biochemical test or by the VITEK 2 GPbiochemical identification test,
22
AOAC Official Method 2012.02 [8].
23
24
Statistical Analysis
25
26
Each collaborating laboratory recorded results for the reference method and the 3M MDA 2 -
27
Listeria monocytogenes
method on the data sheets provided. The data sheets were submitted to
28
the study director at the end of each week of testing for statistical analysis. Data for each matrix
29
was analyzed using the probability of detection (POD)statistical model [9]. The probability of
30
detection (POD) was calculated as the number of positive outcomes divided by the total number
31
of trials. The POD was calculated for the candidate presumptive results, POD
CP,
the candidate
32
confirmatory results (including false negative results), POD
CC
, the difference in the candidate
33
presumptive and confirmatory results, dLPOD
CP,
presumptive candidate results that confirmed
34
positive (excluding false negative results), POD
C,
the reference method, POD
R
, and the
35
difference in the confirmed candidate and reference methods, dLPOD
C
. A dLPOD
C
confidence
36
interval not containing the point zero would indicate a statistically significant difference between
37
the 3M MDA 2 -
Listeria monocytogenes
and the reference methods at the 5 % probability level.
38
In addition to POD, the repeatability standard deviation (s
r
), the among laboratory repeatability
39
standard deviation (s
L
), the reproducibility standard deviation (s
R
)and the P
T
value were
40
calculated. The s
r
provides the variance of data within one laboratory, the s
L
provides the
41
difference in standard deviation between laboratories and the s
R
provides the variance in data
42
between different laboratories. The P
T
value provides information on the homogeneity test of
43
laboratory PODs [10].
44
45
46
47
48
49
AOAC Research Institute
Expert Review Panel Use Only
OMAMAN-30 A/ Collaborative Study Manuscript
OMA ERP June 2016
ERP Use Only