Table 2. Results of the VN test and two ELISAs for the samples with false-negative or false-positive results.
| Category | Horse # | VN titer | Nisseiken-ELISA(sample/cutoff ratioa) | VMRD-ELISA(inhibition indexb) |
|---|---|---|---|---|
| False negative in both ELISAs | 1 | ≥1:512 | − (0.45) | − (6.8) |
| False positive in the Nisseiken-ELISA | 2 | <1:4 | + (1.14) | − (12.0) |
| 3 | <1:4 | + (1.05) | − (5.3) | |
| 4 | <1:4 | + (1.17) | − (9.9) | |
| 5 | <1:4 | + (1.26) | − (−6.5) | |
| 6 | <1:4 | + (1.12) | − (13.4) | |
| 7 | <1:4 | + (1.62) | − (−29.7) | |
| 8 | <1:4 | + (1.67) | − (12.7) | |
| 9 | <1:4 | + (1.32) | − (4.6) | |
| 10 | <1:4 | + (1.96) | − (−22.4) | |
| 11 | <1:4 | + (3.95) | − (4.3) | |
| 12 | <1:4 | + (1.00) | − (7.0) | |
| 13 | <1:4 | + (2.27) | − (−1.7) | |
| 14 | <1:4 | + (1.53) | − (25.6) | |
| 15 | <1:4 | + (4.38) | − (9.9) | |
| 16 | <1:4 | + (2.36) | − (−17.9) | |
| 17 | <1:4 | + (1.01) | − (−3.7) | |
| 18 | <1:4 | + (1.00) | − (16.6) | |
| 19 | <1:4 | + (1.16) | − (5.9) | |
| 20 | <1:4 | + (1.04) | − (11.6) | |
| 21 | <1:4 | + (1.25) | − (−30.7) | |
| 22 | <1:4 | + (1.09) | − (−7.6) | |
| 23 | <1:4 | + (1.22) | − (−3.1) | |
| 24 | <1:4 | + (4.01) | − (14.4) | |
| False positive in the VMRD-ELISA | 25 | <1:4 | − (0.39) | + (46.4) |
| 26 | <1:4 | − (0.34) | + (39.1) | |
| 27 | <1:4 | − (0.42) | + (39.8) |
aSample/cutoff ratio=sample OD/cutoff OD. A ratio ≥1.00 was regarded as positive. bInhibition index=100[1−(sample OD/negative control OD)]. An index ≥35.0 was regarded as positive.