TABLE 3.
Diagnostic value of different numbers of positive specimens
| Microbiology result | Group (no. of patients)a | No. of patients with the following histology result:
|
LR for positive result | Posttest probability of infection (%) | |
|---|---|---|---|---|---|
| Positive | Negative | ||||
| Three or more specimens positive (same organism) | A (297) | 27 | 1 | 169 | 96.4 |
| B (213) | 18 | 1 | 114 | 94.8 | |
| C (239) | 23 | 1 | 144 | 95.8 | |
| Two or more specimens positive (same organism) | A | 2 | 6 | 2.1 | 25.2 |
| B | 1 | 4 | 1.6 | 20.4 | |
| C | 1 | 5 | 1.3 | 17.2 | |
| One positive specimen | A | 5 | 42 | 0.74 | 10.6 |
| B | 5 | 33 | 0.96 | 13.3 | |
| C | 4 | 34 | 0.73 | 10.5 | |
| No growth from any specimen | A | 7 | 207 | 0.21 | 3.3 |
| B | 5 | 146 | 0.22 | 3.4 | |
| C | 5 | 166 | 0.19 | 3.0 | |
a
Group A, whole group; group B, patients for whom three to six samples were sent; group C, patients operated on by most consistent surgeons (interquartile range for number of samples sent per patient, <2).