Microbiology Methods for ERP Review 3-2020

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2011.17) [8] or Bruker MALDI Biotyper (AOAC Official Method 2017.09). In addition to following the confirmation as outlined in the reference method, all Solus test portions were also confirmed following an alternative confirmation procedure. Regardless of presumptive results, all Solus primary enrichments were directly streaked to XLD and Brilliance Salmonella Agar (BSA). Each agar was observed for typical colonies and confirmed following the FDA/BAM Chapter 5 reference method. For the reference method test portions, 25 g samples were enriched in Brilliant Green Water (supplemented with 2% Brilliant Green Dye solution) and analyzed according to the procedures in the FDA/BAM Chapter 5 reference method as described in the preceding paragraph. Each collaborating laboratory reported the test results on the data sheets provided. The data sheets were submitted to the study director at the end of testing for statistical analysis. Data for each contamination level was analyzed using the probability of detection (POD) statistical model [9] and conducted using the AOAC Binary Data Interlaboratory Study Workbook (Version 2.3) [10]. For each laboratory, the POD was calculated for the candidate presumptive results, POD CP, the candidate confirmatory results (including false negative results), POD CC , presumptive candidate results that confirmed positive (excluding false negative results), POD C, and the reference method, POD R . LPOD values, POD values obtained from combining all valid collaborator POD data, were determined for candidate presumptive results, LPOD CP , candidate confirmed results (including false negative results) LPOD CC, presumptive candidate results that confirmed positive (excluding false negative results), LPOD C , and reference method results, LPOD R . Using LPOD values, the dLPOD CP, the difference in the candidate presumptive and confirmatory results from all collaborators and the dLPOD C , the difference in the confirmed candidate and reference methods were calculated. A dLPOD C confidence interval not containing the point zero would indicate a statistically significant difference between the Solus One Salmonella method and the reference method at the 5% probability level. In addition to POD and LPOD values, the repeatability standard deviation (s r ), the among laboratory repeatability standard deviation (s), the reproducibility standard deviation (s R ) and the P T value were calculated [10]. The s r provides the standard deviation of data within one laboratory, the s L provides the difference in standard deviation between laboratories and the s R provides the standard deviation in data between different laboratories. The P T value provides information on the homogeneity of the test portions sent to the laboratories. Statistical Analysis

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