4. AOACRIMicroMethods-2018Awards

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B ird et al .: J ournal of AOAC I nternational V ol . 96, N o . 4, 2013  815

Table 1. Participation of each collaborating laboratory a

+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. 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 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. Alternative Confirmation with IBISA and ASAP

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

Lab

1 2 3 4 5 6 7 8 9

Y Y Y Y Y Y Y Y Y Y Y Y N

Y Y Y Y Y Y Y Y Y Y Y Y N

Y

Y Y Y Y

Y c

Y Y

Y c

Y c

Y Y

Y Y

Y c

Y c

Y c

Y c

Y Y Y Y Y N Y

Y Y Y

10 11 12 13 14 15

Y c

Y c

Y c

Y N

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. 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 ≥0.25

Negative Positive

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