Table 3.
Reclassification: comparison of diagnostic risk for presence of pneumonia by diagnostic model with and without addition of measurement of C reactive protein (CRP). Figures are numbers of patients (%)
| Risk according to “symptoms and signs” model (without CRP) |
Risk according to “symptoms and signs” model plus CRP >30 mg/L | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Patients with pneumonia | Patients without pneumonia | ||||||||
| <2.5% | 2.5-20% | >20% | Total | <2.5% | 2.5-20% | >20% | Total | ||
| <2.5% | 4 (36)* | 7 (64) | 0 (0) | 11 | 568 (87) | 86 (13) | 0 (0) | 654 | |
| 2.5-20% | 27 (26) | 56 (53)* | 22 (21) | 105 | 957 (48) | 966 (49) | 64 (3) | 1987 | |
| >20% | 0 (0) | 5 (21) | 19 (79)* | 24 | 0 (0) | 12 (31) | 27 (69) | 39 | |
| Total | 31 | 68 | 41 | 140 | 1525 | 1064 | 91 | 2680 | |
*Patients classified in agreement according to model with and without CRP >30 mg/L. Of all patients with pneumonia 29 (22+7+0) are reclassified to higher risk groups, and 32 (27+5) to lower risk groups. For patients without pneumonia this is 150 (86+64) and 969 (957+12), respectively. Reclassification improvement is −2% among patients with pneumonia (29-32 of 140) and 30% among patients without pneumonia (957-150 of 2680), resulting in net reclassification improvement of −2+30=28% (95% CI 0.17 to 0.40).