Table 2.
The apparent and true prevalence of PRRSV antibody with Pearson chi-square test in different stages of pigs.
| Background | No. of positive samples | No. of total samples | Apparent prevalence with 95% CI (%) | True prevalence with 95% CI (%) | χ2 values | P value |
|---|---|---|---|---|---|---|
| Piglets (≤21 days) | 666 | 1,401 | 47.537 (44.894–50.191) | 48.062 (45.384–50.751) | 769.570 | <2.2 × 10−16*** |
| Weaned piglets (22–70 days) | 1,149 | 2,682 | 42.841 (40.958–44.740) | 43.304 (41.400–45.228) | ||
| Growing-finishing pigs (≥71 days) | 1,366 | 1,953 | 69.944 (67.856–71.972) | 70.764 (68.648–72.818) | ||
| Replacement gilts | 989 | 1,326 | 74.585 (72.151–76.910) | 75.466 (73.000–77.821) | ||
| Multiparous sows (≥1 parity) | 3,360 | 4,838 | 69.450 (68.130–70.746) | 70.264 (68.927–71.577) | ||
| Boar | 1,211 | 1,934 | 62.616(60.416–64.778) | 63.340(61.111–65.530) | ||
| Total | 8,741 | 14,134 | 61.84 (61.04–62.65) | 62.56 (61.74–63.37) |
CI, confidence interval.
*p < 0.05;
**p < 0.01;
***
p < 0.001.