386 / 1195
3M Molecular Detection Assay Salmonella Collaborative Study
July 2012
OMA-2012-July-XXX
confirmation test using your preferred method or as specified by local
1
regulations.
2
3
5.7
Confirmation
4
All positive 3M Molecular Detection Assay
Salmonella
results must be
5
confirmed. Confirmation should be performed using the primary enrichment and
6
should be initiated within 72 hrs. Isolate on a selective agar and identify 1 to 5
7
typical colonies according to the conventional tests described in the FDA BAM or
8
USDA/FSIS MLG.
9
10
6.0
Reporting Raw Data
11
12
6.1
Report data using the data report form in Appendix 8.2.
13
14
6.2
Upon completion of each food type, the laboratory will fax or email the
15
completed data form to the Study Director.
16
17
6.3
Copies of all related test results (data sheets, printouts and confirmation results)
18
should be retained by the collaborating labs for a minimum of one year.
19
20
7.0
Analyzing Raw Data
21
22
The resulting data will be analyzed by probability of detection (POD).
23
24
7.1
Probability of Detection (POD) -
POD is the proportion of positive analytical
25
outcomes for a qualitative method for a given matrix at a given analyte level or
26
concentration. POD is concentration dependent. Please see the revised
27
microbiology guidelines
3for complete analysis information on POD calculations.
28
29
7.1.1
Calculate:
30
7.1.1.1 Estimate of repeatability - standard deviation (s
r
)
31
7.1.1.2 Determine POD values for each matrix and concentration -
the
32
number of positive outcomes divided by the total number of trials.
33
7.1.1.3 Estimate of reproducibility – standard deviation of the laboratory
34
POD values (s
POD
) and confidence intervals.
35
7.1.1.4 Cross laboratory probability of detection (LPOD) – LPODs by
36
matrix and concentration with 95% confidence intervals for
37
candidate method (presumptive and confirmed) results.
38
7.1.1.5 Difference of cross-laboratory probability of detection (dLPOD) –
39
difference probability of detection is the difference between any
40
two LPOD values.
41
7.1.1.5.1
Estimate dLPOD
C
as the difference between the
42
candidate and reference LPOD values, include CIs.
43
3
AOAC INTERNATIONAL Methods Committee Guidelines for Validation of Microbiological Methods for
Food
and Environmental Surfaces (pre-publication document, 2012) Sharon Brunelle, Robert LaBudde, Maria Nelson,
and Paul Wehling
DRAFT DOCUMENT
10