487 / 596
15
each analysis. Laboratory 11 did not participate in the evaluation of this matrix. Laboratory 10
1
submitted data that indicated cross contamination of the inoculating organism in the un-
2
inoculated control samples. Further analysis at the coordinating laboratory confirmed the cross
3
contamination of the un-inoculated controls. Due to this issue, the data submitted from
4
Laboratory 10 was not used in the statistical analysis. All other laboratories submitted data for
5
both methods evaluated. The MPN levels obtained for this matrix, with 95% confidence
6
intervals, were 0.66 CFU/test portion (0.51, 0.83) for the low level and 6.24 CFU/test portion
7
(3.58, 10.88) for the high level.
8
For the low inoculum level, 86 out of 132 test portions (POD
CP
of 0
.
65) were reported as
9
presumptive positive by the 3M MDA 2 –
Listeria monocytogenes
method with 86out of 132 test
10
portions (POD
CC
of 0.65) confirming positive. For samples that produced presumptive positive
11
results on the 3M MDA 2 –
Listeria monocytogenes
method, 85out of 132 test portions confirmed
12
positive (POD
C
of 0.64). For test portions evaluated by the USDA/FSIS MLGreference method,
13
64 out of 132 test portions produced positive results. A dLPOD
C
value of 0.16 with 95%
14
confidence intervals of (0.04, 0.28) was obtained between the candidate and reference method,
15
indicating a statistically significant difference between the two methods, with a positive
16
correlation in data indicating more recovery of the target analyte by the candidate method. A
17
dLPOD
CP
value of 0.00 with 95% confidence intervals of (-0.12, 0.12) was obtained between
18
presumptive and confirmed results indicating
the difference between presumptive and confirmed
19
methods was not statistically significant at the 0.05 probability
level.nostatistically significant
20
difference between the presumptive and confirmed results.
21
For the high inoculum level, 129 out of 132 test portions (POD
CP
of 0.98) were reported as
22
presumptive positive by the 3M MDA 2 –
Listeria monocytogenes
method with 132out of 132
23
test portions (POD
CC
of 1.00) confirming positive. For samples that produced presumptive
24
positive results on the 3M MDA 2 –
Listeria monocytogenes
method, 129out of 132 samples
25
confirmed positive (POD
C
of 0.98). For test portions evaluated by the USDA/FSIS-MLG
26
reference method, 132 out of 132 test portions produced positive results. A dLPOD
C
value of
27
-0.02 with 95% confidence intervals of (-0.06, 0.01) was obtained between the candidate and
28
reference method, indicating
the difference between methods was not statistically significant at
29
the 0.05 probability
level.nostatistically significant difference between the two methods.
A
30
dLPOD
CP
value of -0.02 with 95% confidence intervals of (-0.06, 0.01) was obtained between
31
presumptive and confirmed results
indicating the difference between presumptive and confirmed
32
methods was not statistically significant at the 0.05 probability level.indicating no statistically
33
significant difference between the presumptive and confirmed results.
34
For the un-inoculated controls, 0 out of 132 samples (POD
CP
of 0.00) produced a presumptive
35
positive result by the 3M MDA 2 -
Listeria monocytogenes
method with 0 out of 132 test
36
portions (POD
CC
of 0.00) confirming positive. For samples that produced presumptive positive
37
results on the 3M MDA 2 –
Listeria monocytogenes
method, 0 out of 132 samples confirmed
38
positive (POD
C
of 0.00). For test portions evaluated by the USDA/FSIS MLG reference method,
39
0 out of 132 test portions produced positive results. A dLPOD
C
value of 0.00 with 95%
40
confidence intervals of (-0.03, 0.03) was obtained between the candidate and reference method,
41
indicating
the difference between methods was not statistically significant at the 0.05 probability
42
level.nostatistical significant difference between the two methods.
A dLPOD
CP
value of 0.00
43