Table 3.
Predictive performance of the four instruments.
| Positive predictive values, % (n) | |||||||
|---|---|---|---|---|---|---|---|
| AUC-I ‘original’ | AUC-II ‘3 categories’ | Cut-offs (n), sensitivity (%), and specificity (%) | Low risk | Medium risk | High risk | ||
| Risk estimation by GP (n = 283a) | 0.59 (0.52 to 0.66) | 0.58 (0.51 to 0.65) | Cut-off ≥1 Sensitivity = 86 Specificity = 17 | Cut-off ≥4 Sensitivity = 28 Specificity = 87 | 33.3 (45) | 33.0 (185) | 56.6 (53) |
| Örebro questionnaire (n = 296a) | 0.61 (0.54 to 0.67) | 0.58 (0.51 to 0.65) | Cut-off >68 Sensitivity = 79 Specificity = 26 | Cut-off >99 Sensitivity = 35 Specificity = 81 | 32.4 (71) | 32.7 (150) | 52.0 (75) |
| Linton (2002)b | 0.61 (0.54 to 0.68) | Cut-off ≥90b Sensitivity = 52 Specificity = 66 | Cut-off >105b Sensitivity = 28 Specificity = 89 | 30.3 (175) | 39.1 (69) | 59.6 (52) | |
| Low Back Pain Perception Scale (n = 298a) | 0.59 (0.52 to 0.66) | 0.57 (0.50 to 0.64) | Cut-off ≥2 Sensitivity = 80 Specificity = 27 | Cut-off ≥4 Sensitivity = 30 Specificity = 81 | 30.1 (73) | 36.1 (155) | 48.6 (70) |
| Prediction rule (n = 267a) | 0.75 (0.69 to 0.81) | 0.72 (0.66 to 0.79) | Cut-off ≥0.28 Sensitivity = 79 Specificity = 55 | Cut-off ≥0.41 Sensitivity = 57 Specificity = 81 | 18.6 (113) | 33.3 (66) | 63.6 (88) |
a
Incidental missing values 9.9% (GP estimation), 5.7% (Örebro questionnaire), 5.1% (Low Back Pain Perception Scale), and 15% (prediction rule).
b
Cut-off scores recommended by Linton.27 AUC = area under the curve.