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CONFIDENTIAL INFORMATION
Page 14 of 17
Table 9. POD
CP
, POD
CC
, and dPOD
CP
Values for the Candidate Method (25 g
Sprouts Analyzed via the 3M
TM
MDA) and POD
R
, POD
C
, and dPOD
C
Values
for Candidate Method vs. the Reference Method (25 g Sprouts Analyzed via
the FDA BAM Ch. 4A)
POD
CP
, Probability of Detection for Candidate Method “Screening Stage” Positive Results; POD
CC
, Probability of
Detection for Candidate Method “Confirmation Stage” Results; dPOD
CP
, POD
CP
Minus POD
CC
; POD
R
, Probability of
Detection for Reference Method Confirmed Results; POD
C
, Probability of Detection for Candidate Method
Confirmed Results (i.e. Combined “Screening Stage” and “Confirmation Stage” Results); dPOD
C
, POD
R
Minus
POD
C
. 95% Confidence Interval Values are Generated from the AOAC International POD Calculator.
4.0 DISCUSSION
The purpose of this study was to validate the
3M™
Molecular Detection Assay
(MDA) for detection of
Escherichia coli
O157:H7 in sprouts and spinach. This
study followed the format for the validation of a candidate method using the
experimental setup and Probability of Detection (POD) statistical analysis provided
in the February 24, 2012 version of the AOAC International Methods Committee
Guidelines for Validation of Microbiological Methods for Food and Environmental
Surfaces document (1). Portions of spinach (200 g sample size) and sprouts (25
Method / Inoculation Level
Measure Value
95% CI
POD
CP
0.800 (0.3755, 1.000)
POD
CC
0.800 (0.3755, 1.000)
dPOD
CP
0.000 (-0.469, 0.469)
POD
CP
0.500 (0.2993, 0.7007)
POD
CC
0.500 (0.2993, 0.7007)
dPOD
CP
0.000 (-0.284, 0.284)
POD
CP
0.000 (0.000, 0.4345)
POD
CC
0.000 (0.000, 0.4345)
dPOD
CP
0.000 (-0.434, 0.434)
POD
R
1.000 (0.5655, 1.000)
POD
C
0.800 (0.3755, 1.000)
dPOD
C
-0.200 (-0.624, 0.278)
POD
R
0.350 (0.1812, 0.5672)
POD
C
0.500 (0.2993, 0.7007)
dPOD
C
0.150 (-0.146, 0.412)
POD
R
0.000 (0.000, 0.4345)
POD
C
0.000 (0.000, 0.4345)
dPOD
C
0.000 (-0.434, 0.434)
Reference Method vs. Candidate Method High Level
Inoculation
Reference Method vs. Candidate Method Low Level Inoculation
Reference Method vs. Candidate Method Un-inoculated
Candidate Method Screening vs. Confirmation High Level
Inoculation
Candidate Method Screening vs. Confirmation Low Level
Inoculation
Candidate Method Screening vs. Confirmation Un-inoculated