Inter-laboratory comparison of 2 ELISA kits used for foot-and-mouth disease virus nonstructural protein serology

Figures

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  Figure 1.. Status of samples used in the study of 2 FMDV NSP ELISA kits. Results were obtained from testing the panel of sera (n = 180) with the ELISAs used in the inter-laboratory exercise. The true-negative and true-positive status of the serum (y-axis) was defined by the history of the animal. The test response was calculated: PI(100 – [mean sample OD/mean OD of negative control] × 100) for the PrioCHECK results, and normalized sample-to-negative ratio for the ID Screen assays: (100 – [mean sample OD/mean OD of negative control] × 100).

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  Figure 2.. Comparative analysis of the operators and laboratories for each of the FMDV NSP ELISAs. The Cohen kappa statistic test was used to analyze the variation between laboratories and operators. For the top panels, the x- and y-axes represent the 5 laboratories. For the bottom panels, the x- and y-axes represent the 2 operators from each laboratory (denoted A–E). Colors denote concordance between operators or laboratories.

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  Figure 3.. Concordance of the results of the 2 ID Screen FMDV NSP ELISA kits with the PrioCHECK ELISA. The mean is plotted of duplicate determinations by each operator in the participating laboratories. The true positives (red) and the true negatives (open circles) were determined by the animal status. The left panel compares the ID Screen overnight (y-axis) and the PrioCHECK (x-axis). The right panel compares results for the ID Screen short against PrioCHECK. The red dashed lines define the cutoff for each assay.