Results of Spearman correlation analysis between potential confounding factors and D
| Predictor | Coefficient | p Value |
| Percentage of patients with LOC/PTA (selection bias) | −0.6792 | 0.011 |
| Percentage of CT scans (verification bias) | −0.6472 | 0.017 |
| Skull radiograph compared with CT for fracture diagnosis | 0.2535 | 0.403 |
| Prospective studies v retrospective studies | 0.4900 | 0.089 |
| Adult populationv all ages | 0.0976 | 0.751 |
See equation 4 for the definition of D.