Table 2.
Sample size to achieve a Confidence level of 95% (probability of detecting or ruling out the presence of LSD) in an establishment by using PCR on blood in EDTA, assuming a low design prevalence of 1%. The median sensitivity of PCR methods is used for blood and swabs, respectively
| Herd size | PCR on blood in EDTA (Se = 95.25%) | PCR on oral/nasal/ophthalmic swab (Se = 97.75%) | ||||
|---|---|---|---|---|---|---|
| Design prevalence | Sample size | Confidence | Design prevalence | Sample size | Confidence | |
| 10 | 10%* | 10 | 95% | 10%* | 10 | 98% |
| 20 | 5%* | 20 | 95% | 5%* | 20 | 98% |
| 50 | 2%* | 50 | 95% | 2%* | 49 | 96% |
| 100 | 1% | 100 | 95% | 1% | 98 | 96% |
| 200 | 1% | 163 | 95% | 1% | 159 | 95% |
| 250 | 1% | 204 | 95% | 1% | 199 | 95% |
| 300 | 1% | 199 | 95% | 1% | 194 | 95% |
| 500 | 1% | 236 | 95% | 1% | 230 | 95% |
| 750 | 1% | 245 | 95% | 1% | 239 | 95% |
| 1000 | 1% | 271 | 95% | 1% | 264 | 95% |
*
The minimum number of animals being infected in a herd is one. Therefore, the values for the design prevalence provided here are the result of the ratio between 1 and the herd size.