Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of risk criteria count (cumulative) and independent risk criteria in total patient cohort (n=20 109)
| Sensitivity | (95% CI) | Specificity | (95% CI) | PPV | (95% CI) | NPV | (95% CI) | |
| Risk criteria count | ||||||||
| 0 | – | – | – | – | ||||
| 1 | 3.5 | (3.2 to to 3.9) | 100.0 | (99.9 to 100.0) | 99.0 | (97.3 to 99.7) | 47.2 | (46.5 to 47.9) |
| 2 | 8.4 | (7.6 to 9.4) | 99.6 | (99.5 to 99.7) | 84.3 | (80.3 to 87.8) | 82.2 | (81.7 to 82.8) |
| 3 | 17.1 | (15.1 to 19.3) | 99.1 | (99.0 to 99.3) | 58.0 | (52.8 to 63.0) | 94.6 | (94.2 to 94.9) |
| 4 | 26.3 | (22.0 to 30.9) | 98.6 | (98.4 to 98.7) | 27.2 | (22.8 to 31.9) | 98.5 | (98.3 to 98.7) |
| 5 | 36.6 | (26.2 to 48.0) | 98.2 | (98.0 to 98.4) | 7.8 | (5.3 to 11.0) | 99.7 | (99.7 to 99.8) |
| 6 | 57.1 | (18.4 to 90.1) | 98.1 | (97.9 to 98.3) | 1.0 | (0.3 to 2.7) | 100.0 | (100.0 to 100.0) |
| 7 | – | – | – | – | ||||
| Risk criteria | ||||||||
| 1. Evidence of skull fracture | 10.6 | (9.3 to 12.0) | 99.1 | (98.9 to 99.2) | 56.4 | (51.3 to 61.4) | 90.8 | (90.4 to 91.2) |
| 2. Scalp haematoma | 4.1 | (3.6 to 4.7) | 99.0 | (98.8 to 99.2) | 62.4 | (57.3 to 67.3) | 71.8 | (71.1 to 72.4) |
| 3. Neurological deficits | 6.5 | (4.7 to 8.8) | 98.2 | (98.1 to 98.4) | 10.7 | (7.8 to 14.2) | 97.0 | (96.8 to 97.3) |
| 4. Altered levels of alertness | 12.4 | (10.9 to 13.9) | 99.2 | (99.0 to 99.3) | 61.4 | (56.3 to 66.3) | 91.6 | (91.2 to 92.0) |
| 5. Abnormal behaviour | 6.1 | (5.3 to 6.9) | 99.0 | (98.8 to 99.1) | 56.9 | (51.8 to 61.9) | 82.9 | (82.3 to 83.4) |
| 6. Persistent vomiting | 4.8 | (3.9 to 5.8) | 98.4 | (98.2 to 98.6) | 26.4 | (22.0 to 31.1) | 89.8 | (89.3 to 90.2) |
| 7. Coagulopathy | 3.8 | (2.0 to 6.5) | 98.1 | (97.9 to 98.3) | 3.1 | (1.6 to 5.4) | 98.5 | (98.3 to 98.6) |