Table 2.
Primary analysis for the performance* of the Widal test for typhoid fever diagnosis (n = 1680)
| Widal titer | Sensitivity (95%CI) | Specificity (95%CI) | Positive Predictive Value | Negative Predictive Value |
|---|---|---|---|---|
| TH ≥1:80 | 12/16, 0.75 (0.51-0.90) |
1630/1664, 0.98 (0.97-0.99) |
12/46, 0.26 | 1630/1634, 1.00 |
| TH ≥1:160 | 11/16, 0.69 (0.44-0.86) |
1639/1664, 0.98 (0.98-0.99) |
11/36, 0.31 | 1639/1644, 1.00 |
| TH ≥1:320 | 6/16, 0.38 (0.18-0.61) |
1646/1664, 0.99 (0.98-0.99) |
6/24, 0.25 | 1646/1656, 0.99 |
| TO ≥1:80 | 11/16, 0.69 (0.44-0.86) |
1631/1664, 0.98 (0.97-0.99) |
11/44, 0.25 | 1631/1636, 1.00 |
| TO ≥1:160 | 10/16, 0.63 (0.39-0.82) |
1640/1664, 0.99 (0.98-0.99) |
10/34, 0.29 | 1640/1646, 1.00 |
| TO ≥1:320 | 6/16, 0.38 (0.18-0.61) |
1652/1664, 0.99 (0.99-1.00) |
6/18, 0.33 | 1652/1662, 0.99 |
*The values were calculated using culture-confirmed typhoid fever cases (group 1; n = 16) as the true positives and those cases from which S. typhi were not isolated from blood culture (groups 2, 3, and 4; n = 1664) as the true negatives.