Table 2.
Characteristics of the chest X-ray as test for identification of patients with a bacterial infection.
| Radiographic findings | ||
|---|---|---|
| Pneumonia, % (95% CI) | Signs of infection, % (95% CI) | |
| At observed prevalence (41/84) | ||
| Sensitivity | 29 (16 to 46) | 46 (31 to 63) |
| Specificity | 91 (75 to 97) | 79 (64 to 90) |
| Positive predictive value | 75 (48 to 93) | 68 (48 to 84) |
| Negative predictive value | 57 (45 to 69) | 61 (47 to 74) |
| At maximum prevalence (86/129)a | ||
| Positive predictive value | 85 (65 to 96) | 80 (65 to 90) |
| Negative predictive value | 38 (29 to 47) | 41 (30 to 52) |
| At minimal prevalence (41/129)a | ||
| Positive predictive value | 46 (27 to 65) | 42 (28 to 58) |
| Negative predictive value | 72 (63 to 81) | 74 (63 to 83) |
a
For the ‘maximum prevalence’ all aetiological unknown cases were considered as of bacterial origin, and for the ‘minimal prevalence’ these cases were considered as of viral origin.