Validation of S-iELISA
To analysis the specificity and sensitivity of S-iELISA, a total of 111 pig serum samples were tested by IFA (Fig 5A) and S-iELISA, respectively. As shown in Fig 5B, the IFA detected 92 SADS-CoV-positive samples, of which 90 tested SADS-CoV-positive by S-iELISA. On the other hand, of the remaining 19 samples that tested SADS-CoV-seronegative by IFA, 18 of them were tested SADS-CoV-negative by S-iELISA. Hence, the sensitivity of S-iELISA was 97.8% among SADS-CoV-seropositive individuals, and the specificity was 94.7% among SADS-CoV-seronegative individuals using IFA as standard evaluation method. These results suggest that the overall coincidence rate of the S-iELISA to IFA was 97.3%.