| Initial CT | ||
| Yes | No | |
| Clinician accuracy of initial CT scan in ED (n=20 109) | ||
| Positive ICI | 377 | 0 |
| Negative ICI | 1585 | 18 147 |
| Sensitivity (95% CI) | 377/377 | 100.0 (99.0 to 100.0) |
| Specificity (95% CI) | 18 147/19 732 | 92.0 (91.6 to 92.3) |
| PPV (95% CI) | 377/1962 | 19.2 (17.5 to 21.0) |
| NPV (95% CI) | 18 147/18 147 | 100.0 (100.0 to 100.0) |
ICI, intracranial injury; NEXUS, National Emergency X-Radiography Utilisation Study; NPV, negative predictive value; PPV, positive predictive value.