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3M MDA2 E. coli O157:H7 Collaborative Study
May 2016
OMA-2016-May-XXXX
DRAFT DOCUMENT
9
1
c)
Copies of all related test results (data sheets and confirmation results) should be retained by the
2
collaborating labs for a minimum of one year.
3
4
5)
Analyzing Raw Data
5
6
a)
The resulting data will be analyzed by two different calculations: probability of detection (POD).
7
8
b)
Probability of Detection (POD) -
POD is the proportion of positive analytical outcomes for a
9
qualitative method for a given matrix at a given analyte level or concentration. POD is
10
concentration dependent. Please see the revised microbiology guidelines
1
for complete analysis
11
information on POD calculations.
12
13
a)
Calculate:
14
(1)
Estimate of repeatability - standard deviation (s
r
)
15
(2)
Determine POD values for each matrix and concentration -
the number of positive
16
outcomes divided by the total number of trials.
17
(3)
Estimate of reproducibility – standard deviation of the laboratory POD values (s
POD
) and
18
confidence intervals.
19
(4)
Cross laboratory probability of detection (LPOD) – LPODs by matrix and concentration
20
with 95% confidence intervals for candidate method (presumptive and confirmed)
21
results.
22
(5)
Difference of cross-laboratory probability of detection (dLPOD) – difference probability
23
of detection is the difference between any two LPOD values.
24
(a)
Estimate dLPOD
C
as the difference between the candidate and reference LPOD
25
values, include CIs.
26
(b)
Estimate dLPOD
CP
as the difference between the presumptive and confirmed LPOD
27
values, include CIs.
28
(c)
If the CI of a dLPOD does not contain zero then the difference is statistically
29
significant
.
30
(6)
For each matrix,
graph POD
R
, LPOD
C
and dLPOD
C
by level with 95% confidence intervals.
31
32
6)
Appendices
33
34
a)
Instructions to Collaborators
35
b)
Test Portion Data Report Forms
36
c)
Study Materials
37
d)
Flow Diagram – raw ground beef (325 g)
38
Appendix 8.1
39
40
Instructions to Collaborators
41
42
General Instructions about Collaborative Studies
43
44
1
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
OMAMAN-35 B: Collaborative Study Protocol
ERP USE ONLY
January 2017
AOAC Research Institute
Expert Review Panel Use Only