Table 1. Diagnostic performances of three serological tests used to detect Schmallenberg virus antibodies from samples of known status with inclusion of suspect/doubtful in the negative results (a) and in the positive results (b).
| a) Suspect/doubtful included in the negative results | |||||
| SNT | IDEXX | ID.Vet | |||
| Infected (n = 45) | |||||
| *True positive | 45 | 35 | 43 | ||
| False negative | 0 | 10 | 2 | ||
| Uninfected (n = 45) | |||||
| **True negative | 45 | 44 | 45 | ||
| False positive | 0 | 1 | 0 | ||
| Seroprevalence (%) | 50 (39–61) | 40 (30–51) | 48 (37–59) | ||
| Sensitivity (%) | 100 (92–100) | 78 (63–89) | 96 (85–99) | ||
| Specificity (%) | 100 (92–100) | 98 (88–100) | 100 (92–100) | ||
| J | 1 | 0.75 | 0.96 | ||
| κ† | 1 (0.105) | 0.75 (0.103) | 0.96 (0.105) | ||
| b) Suspect/doubtful included in the positive results | |||||
| SNT | IDEXX | ID.Vet | |||
| Infected (n = 45) | |||||
| *True positive | 45 | 42 | 45 | ||
| False negative | 0 | 3 | 0 | ||
| Uninfected (n = 45) | |||||
| **True negative | 45 | 42 | 45 | ||
| False positive | 0 | 3 | 0 | ||
| Seroprevalence (%) | 50 (39–61) | 58 (47–68) | 50 (39–61) | ||
| Sensitivity (%) | 100 (92–100) | 93 (82–99) | 100 (92–100) | ||
| Specificity (%) | 100 (92–100) | 93 (82–99) | 100 (92–100) | ||
| J | 1 | 0.86 | 1 | ||
| κ† | 1 (0.105) | 0.86 (0.105) | 1 (0.105) | ||
Abbreviations: SBV—Schmallenberg virus, J—Youden’s index, κ - Cohen’s Kappa
*Serum samples (n = 45) collected during 2012 re-emergence from sheep with a clinical presentation of Schmallenberg virus (SBV) infection (malformed offspring) and confirmed by PCR analysis in the sampled blood represented true positives.
**Serum samples (n = 45) collected from sheep in 2008 before first SBV emergence in Europe represented true negatives. Percentage range of exact 95% confidence intervals (CI) is shown between the brackets.
† For each κ value, the standard error is indicated between the brackets.