ERP Micro December 2019

collaborators recovered the target analyte in their non-inoculated control samples for the reference method (collaborators 8 and 9) and one collaborator recovered the target analyte in their non-inoculated control samples for the candidate method (collaborator 6). Although laboratory testing did not confirm the source of contamination, the empirical evidence suggest that these positive results were attributed to laboratory cross contamination. Collaborator 7 followed all elements of the testing protocol with the exception of prewarming the candidate method LPT enrichment broth. The results however demonstrated that the candidate method accurately detected the target analyte. All data submitted were included in the final statistical analysis. From these 15 collaborators, 3 false positive results were obtained, two for the low-level test portions and one for the non-inoculated test portions. No discordant results were observed with the high-level test portions. The FP and FN rates were calculated as follows:

False Positive Rate = [FP/(True Positives + FP)] x 100

False Negative Rate = [FN/(True Negatives + FN)] x 100

For the data used in the statistical analysis, a false positive rate of 1.4% and a false negative rate of 0.0% were obtained. For the candidate method, variations observed were mainly within laboratory analysis (repeatability) and very little variation was observed between laboratories (reproducibility). No statistically significant differences were observed between the presumptive and confirmed results for the candidate method nor between the candidate and reference methods. Based on the data obtained during the collaborative study, the method was granted certification through the AFNOR NF VALIDATION program.

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