| Patient characteristics | 25% cut-offCRP, mg/L (CI) | 50% cut-offCRP, mg/L (CI) | 75% cut-offCRP, mg/L (CI) |
|---|---|---|---|
| All the patients (n = 4635) | 20 (18 to 22) | 40 (37 to 42) | 50 (47 to 98) |
| Age group, years | |||
| 0–14 | 22 (18 to 67) | 43 (32 to 98) | 45 (43 to 98) |
| 15–64 | 22 (20 to 28) | 42 (38 to 45) | 64 (49 to 99) |
| >64 | 17 (14 to 20) | 33 (24 to 41) | 46 (41 to 98) |
| Fever | |||
| Yes | 20 (17 to 23) | 38 (34 to 41) | 47 (45 to 84) |
| No | 22 (17 to 25) | 45 (36 to 97) | 66 (50 to 99) |
| Symptoms | |||
| Cough | 24 (22 to 27) | 42 (38 to 44) | 64 (49 to 99) |
| Sore throat | 29 (19 to 37) | 45 (38 to 71) | 74 (49 to 99) |
| Ear/face pain | 11 (5 to 12) | 20 (14 to 99) | 40 (37 to 99) |
| Dyspnoea | 11 (8 to 20) | 24 (21 to 99) | 38 (30 to 99) |
| Purulent rhinorrhoea | 14 (13 to 32) | 38 (25 to 99) | 55 (40 to 99) |
| Duration of symptoms, days | |||
| ≤1 | 21 (14 to 89) | 29 (22 to 99) | 53 (29 to 99) |
| 2–4 | 24 (20 to 36) | 43 (41 to 48) | 54 (49 to 98) |
| 5–14 | 17 (15 to 22) | 38 (33 to 61) | 46 (45 to 99) |
| >14 | 15 (14 to 93) | 27 (21 to 93) | 50 (29 to 93) |
| Deterioration of symptoms | |||
| Yes | 14 (11 to 39) | 42 (20 to 99) | 46 (42 to 99) |
| No | 22 (20 to 24) | 41 (37 to 44) | 51 (49 to 98) |
| Poor general appearance | |||
| Yes | 15 (11 to 17) | 29 (22 to 41) | 44 (42 to 85) |
| No | 24 (21 to 29) | 43 (39 to 46) | 66 (51 to 99) |
| Abnormal lung auscultation | |||
| Yes | 3 (1 to 8) | 22 (13 to 27) | 32 (28 to 99) |
| No | 24 (21 to 33) | 45 (42 to 62) | 68 (50 to 99) |
aEstimated as the lowest level of CRP at which the given percentage of patients were prescribed an antibiotic. Values in brackets indicate the 95% CI for the CRP levels ±5 mg/L, based on binomial distribution. CI = confidence interval. CRP = C-reactive protein.