14 / 129
B
ird
et al
.:
J
ournal of
AOAC I
nternational
V
ol
.
96, N
o
. 4, 2013
815
+0.49) was obtained between the USDA/FSIS-MLG method
and the VIDAS SPT method. The confidence intervals obtained
for dLPOD
C
indicated a statistically significant difference
between the two methods. However, the VIDAS SPT method
detected more positive samples than the USDA/FSIS-MLG
reference method, indicating a higher level of sensitivity than
the reference method. A dLPOD
CP
of 0.01 (–0.02, +0.04)
was obtained between presumptive and confirmed VIDAS
SPT results for both confirmation procedures. The confidence
intervals obtained for dLPOD
CP
indicated no significant
difference between the presumptive and confirmed results.
For the high-level inoculum, a dLPOD
C
value of 0.04 (+0.01,
+0.09) was obtained between the USDA/FSIS-MLG method
and the VIDAS SPT method. The confidence intervals obtained
for dLPOD
C
indicated a statistically significant difference
between the two methods. However, the VIDAS SPT method
detected more positive samples than the USDA/FSIS-MLG
reference method, indicating a higher level of sensitivity than
the reference method. A dLPOD
CP
of 0.00 (–0.03, +0.03)
was obtained between presumptive and confirmed VIDAS
SPT results. The confidence intervals obtained for dLPOD
CP
indicated no significant difference between the presumptive
and confirmed results. Detailed results of the POD statistical
analysis are presented in Table
2013.01A
and in appended
Table B and Figure 1C and D.
Alternative Confirmation with IBISA and ASAP
For the high inoculum level, all 144 test portions were
reported as positive by the VIDAS SPT method, with all test
portions confirming positive. For the low inoculum level,
all 144 test portions were also reported as positive by the
VIDAS SPT method, with 143 confirming positive. For the
uninoculated controls, none of the 144 samples produced a
presumptive positive result by the VIDAS SPT method, and all
samples confirming negative. For test portions analyzed by the
USDA/FSIS-MLG method, 138 of the 144 high inoculum test
portions and 84 of the 144 low inoculum test portions confirmed
positive. For the uninoculated controls, none of the 144 test
portions confirmed positive.
For the low level inoculum, a dLPOD
C
value of 0.41 (+0.32,
+0.49) was obtained between the USDA/FSIS-MLG method
and the VIDAS SPT method. The confidence intervals obtained
for dLPOD
C
indicated a statistically significant difference
between the two methods. However, the VIDAS SPT method
detected more positive samples than the USDA/FSIS-MLG
reference method, indicating a higher level of sensitivity than
the reference method A dLPOD
CP
of 0.01 (–0.02, +0.04) was
obtained between presumptive and confirmed VIDAS SPT
results for both confirmation procedures. The confidence
intervals obtained for dLPOD
CP
indicated no significant
difference between the presumptive and confirmed results.
For the high-level inoculum, a dLPOD
C
value of 0.04 (+0.01,
+0.09) was obtained between the USDA/FSIS-MLG method
and the VIDAS SPT method. The confidence intervals obtained
for dLPOD
C
indicated a statistically significant difference
between the two methods. However, the VIDAS SPT method
detected more positive samples than the USDA/FSIS-MLG
reference method, indicating a higher level of sensitivity
than the reference method A dLPOD
CP
of 0.00 (–0.03, +0.03)
was obtained between presumptive and confirmed VIDAS
SPT results. The confidence intervals obtained for dLPOD
CP
indicated no significant difference between the presumptive
and confirmed results. Detailed results of the POD statistical
analysis are presented in Table
2012.01A
and in appended
Table C and Figure 1E and F.
Table 1. Participation of each collaborating laboratory
a
Lab
Raw ground
beef (25 g
test portions)
Raw ground
beef (25 g
test portions)
b
Raw ground
beef (375 g
test portions)
Raw ground
beef (375 g test
portions)
b
1
Y
Y
Y
Y
2
Y
Y
Y
c
Y
3
Y
Y
Y
Y
4
Y
Y
Y
Y
5
Y
Y
Y
c
Y
c
6
Y
Y
Y
Y
7
Y
Y
Y
Y
8
Y
c
Y
c
Y
c
Y
c
9
Y
Y
Y
Y
10
Y
Y
Y
Y
11
Y
Y
Y
Y
12
Y
c
Y
c
Y
Y
c
13
Y
Y
Y
Y
14
Y
Y
N
N
15
N
N
Y
Y
a
Y = Collaborator analyzed the food type; N = collaborator did not
analyze the food type.
b
Results were confirmed following the alternative confirmation
procedure.
c
Results were not used in statistical analysis due to laboratory error, or
uninoculated control test portions were confirmed as
Salmonella
.
Table 2013.01D. Interpretation of test
Test value threshold
Interpretation
<0.25
Negative
≥0.25
Positive
Table 2013.01C. Reagents included in 10-well reagent
strip
Wells
Reagents (SPT)
1
Sample well: 0.5 mL of enrichment broth, standard or control
2
Prewash solution (400 µL): Buffer pH 7.8 + preservative
3–5, 7–9 Wash buffer (600 µL): TRIS-buffered saline (150 mmol/L) –
Tween pH 7.6 + preservative
6
Conjugate (400 µL): alkaline phosphatase-labeled proteins
specific for
Salmonella
receptors + preservative
10
Reading cuvette with substrate (300 µL): 4-methyl-umbelliferyl
phosphate (0.6 mmol/L) + diethanolamine
a
(DEA; 0.62 mol/L
or 6.6%, pH 9.2) + preservative
a
Irritant reagent;
see
VIDAS SPT package insert for more information.
11