Table 5.
Areas under operating receiver characteristic curves and test characteristics (95% confidence intervals) for entire dataset for three risk assessment scales*
| Norton scale | Braden scale | Waterlow scale | |
|---|---|---|---|
| All patients (n=2190 patient weeks) | |||
| Area under curve | 0.56 (0.51 to 0.61) | 0.55 (0.49 to 0.60) | 0.61 (0.56 to 0.66) |
| Sensitivity (%) | 46.2 (37.7 to 54.7) | 43.5 (35.0 to 52.0) | 89.5 (83.8 to 95.1) |
| Specificity (%) | 60.4 (58.3 to 62.6) | 67.8 (65.7 to 69.8) | 22.4 (20.5 to 24.4) |
| Positive predictive value (%) | 7.1 (5.5 to 9.1) | 8.1 (6.2 to 10.3) | 6.7 (5.5 to 8.0) |
| Negative predictive value (%) | 94.5 (93.1 to 95.7) | 94.9 (93.6 to 95.9) | 97.2 (95.1 to 98.5) |
| Subpopulation (n=1355 patient weeks)† | |||
| Area under curve | 0.71 (0.65 to 0.77) | 0.71 (0.64 to 0.78) | 0.68 (0.61 to 0.74) |
| Sensitivity (%) | 78.7 (66.3 to 88.1) | 72.9 (59.7 to 83.6) | 95.9 (86.0 to 99.5) |
| Specificity (%) | 46.5 (43.7 to 49.3) | 57.2 (55.4 to 60.0) | 22.0 (19.5 to 24.5) |
| Positive predictive value (%) | 7.0 (5.2 to 9.2) | 7.8 (5.7 to 10.4) | 5.3 (3.9 to 7.0) |
| Negative predictive value (%) | 97.7 (96.1 to 98.8) | 97.7 (96.3 to 98.7) | 99.2 (97.0 to 99.9) |
*
Cut-off points: at risk if <16 on the Norton scale, <18 on the Braden scale, or >9 on the Waterlow scale.
†
Excluding patient weeks with preventive measures without pressure ulcers and surgical patients.