Calibration of severity scores against predicted mortality from the original derivation studies
| Observed mortality | Predicted mortality | RR (95% CI) | p Value | I2 | |
| PSI | |||||
| I–II | 0.75% | 0.3% | 2.24 (1.27 to 3.96) | 0.005 | 0% |
| I–III | 1.6% | 0.4% | 3.64 (2.72 to 4.87) | <0.00001 | 0% |
| IV | 8.9% | 9.3% | 0.91 (0.79 to 1.06) | 0.2 | 48% |
| V | 28.2% | 27% | 0.99 (0.88 to 1.11) | 0.9 | 57% |
| CURB65 | |||||
| 0–1 | 2.0% | 1.2% | 1.63 (1.11 to 2.40) | 0.01 | 27% |
| 2 | 8.3% | 9% | 0.95 (0.74 to 1.21) | 0.7 | 55% |
| 3–5 | 22.3% | 22.6% | 1.03 (0.84 to 1.25) | 0.8 | 76% |
| CRB65 | |||||
| 0 | 2.3% | 0.9% | 1.15 (0.45 to 2.94) | 0.8 | 52% |
| 1–2 | 13.3% | 8.1% | 1.13 (0.83 to 1.55) | 0.4 | 90% |
| 3–4 | 34.4% | 31.2% | 1.06 (0.91 to 1.23) | 0.5 | 31% |
PSI, Pneumonia Severity Index.