Fig. 3
Determination of the cutoff value, specificity and reproducibility of NS6-iELISA. a PDCoV iELISA cutoff value determination. PDCoV-negative serum samples were tested using the optimized NS6-based ELISA and the cutoff value (dashed line) was calculated as the mean OD450nm value of PDCoV-negative serum samples plus three standard deviations (SD). A representative PDCoV-positive serum sample is shown as control. b Reproducibility of the PDCoV iELISA. 20 control serum samples (16 positive and four negative) were tested repeatedly by the NS6-based iELISA, and the OD450nm values of the serum samples were used to calculate the coefficient of variation (CV), showing the intra- and interassay reproducibility. c PDCoV iELISA specificity. Positive control serum samples for PEDV, SADS-CoV and TGEV were tested by the NS6-based iELISA method; PDCoV positive and negative sera were included as controls