111 / 596
15
significant difference between the two methods, with a positive with a positive correlation in
1
data indicating more recovery of the target analyte by the candidate method. A dLPOD
CP
value
2
of 0.02 with 95% confidence intervals of (-0.10, 0.13) was obtained between presumptive and
3
confirmed results indicating no statistically significant difference between the presumptive and
4
confirmed results.
5
For the high inoculum level, 131 out of 132 test portions (POD
CP
of 0.99) were reported as
6
presumptive positive by the 3M MDA 2 –
Listeria
method with 132out of 132 test portions
7
(POD
CC
of 1.00) confirming positive. For samples that produced presumptive positive results on
8
the 3M MDA 2 –
Listeria
method, 131out of 132 samples confirmed positive (POD
C
of 0.99).
9
For test portions evaluated by the USDA/FSIS-MLG reference method, 132 out of 132 test
10
portions produced positive results. A dLPOD
C
value of -0.01 with 95% confidence intervals of
11
(-0.04, 0.02) was obtained between the candidate and reference method, indicating no
12
statistically significant difference between the two methods. A dLPOD
CP
value of -0.01 with
13
95% confidence intervals of (-0.04, 0.02) was obtained between presumptive and confirmed
14
results indicating no statistically significant difference between the presumptive and confirmed
15
results.
16
For the un-inoculated controls, 2 out of 132 samples (POD
CP
of 0.02) produced a presumptive
17
positive result by the 3M MDA 2 -
Listeria
method with 1 out of a 132 test portions (POD
CC
of
18
0.01) confirming positive. For samples that produced presumptive positive results on the 3M
19
MDA 2 –
Listeria
method, 1 out of 132 samples confirmed positive (POD
C
of 0.01). For test
20
portions evaluated by the USDA/FSIS-MLG reference method, 0 out of 132 test portions
21
produced positive results. A dLPOD
C
value of 0.01 with 95% confidence intervals of (-0.02,
22
0.04) was obtained between the candidate and reference method, indicating no statistical
23
significant difference between the two methods. A dLPOD
CP
value of 0.01 with 95% confidence
24
intervals of (-0.03, 0.05) was obtained between presumptive and confirmed results indicating no
25
statistically significant difference between the presumptive and confirmed results.
26
27
Detailed results of the POD statistical analysis are presented in Table 2016.2B and Figures 1C-
28
1D.
29
30
Discussion
31
32
No negative feedback was provided by the collaborating laboratories in regard to the
33
performance of the 3M MDA 2-
Listeria
method. During the evaluation of the raw chicken breast
34
fillet, Laboratory 2 isolated
Listeria innocua
from an un-inoculated control sample. Since the
35
organism recovered was different from the inoculating organism,
Listeria monocytogenes,
no
36
just cause for removal of the data was determined and the data was included in the manuscript.
37
For the raw chicken breast fillet, Laboratory 10 reported isolating
Listeria monocytogenes
from
38
two un-inoculated control samples. The isolates were sent for further identification and it was
39
determined that they were the same strain as the inoculating organism, indicating that cross
40
contamination of the sample occurred. Due to the fact that cross contamination occurred, just
41
cause removal of the data was established and the data generated by Laboratory 10 was therefore
42
not included in the statistical analysis.
43
AOAC Research Institute
Expert Review Panel Use Only
OMAMAN-29 A/ Collaboartive Study Manuscript
OMA ERP June 2016
ERP Use Only