Fig. 3

Receiver operating characteristic (ROC) analysis and distribution of the results of the immunostaining and full-length S-based ELISA. a The ROC analysis of the full-length S-based ELISA. The sensitivity and specificity were calculated using negative (n = 213) and positive (n = 90) serum samples. The x axis shows 1-specificity and the y axis shows sensitivity. b The immunostaining titers of immunofluorescence assay of each serum sample are presented as a logarithm with base 10. Serum samples that were negative for the immunostaining are denoted by 0. The results of the full-length S-based ELISA are presented as the S/P ratio. The dotted line represents the cut-off value of an S/P ratio of 0.432 as determined by the ROC analysis. C-N (with grey square icon): conventional PEDV naïve pigs; C-I (with black square icon): experimental PEDV inoculated conventional pigs; SPF-N (with grey round icon): specific pathogen free PEDV naïve pigs; SPF-I (with black round icon): experimental PEDV inoculated SPF pigs; Sow-F (with black triangle icon): PEDV-feedback sows