Table 3.
Multivariate logistic regression analyses resulting in 2 final prediction models
| Variables | OR | 95% CI | P |
|---|---|---|---|
|
One-year U-RTW, final prediction model, N=282 |
|
|
|
| Risk groups: Final combination variable Overall p |
|
|
<0.001 |
| (pain/side-flexion, bodily distress, 4 dichotomous variables2) |
|
|
|
| Low |
1 |
|
|
| Intermediate |
5.04 |
2.11-12.02 |
|
| High |
15.5 |
6.56-36.41 |
|
| Radiculopathy1, ref. non-specific LBP |
0.57 |
0.27-1.120 |
0.138 |
| BMI in non-spec. LBP group, ref. 25 kg/m2 |
0.97 |
0.91-1.03 |
0.305 |
| Effect modification BMI: |
|
|
|
| OR(BMI radiculopathy)/OR(BMI non-specific) |
1.33 |
1.12-1.57 |
0.001 |
| Age in non-spec. LBP group, ref. 40 years |
0.99 |
0.96-1.03 |
0.589 |
| Effect modification age: |
|
|
|
| OR(age radiculopathy)/ OR(age non-specific) |
1.08 |
1.01-1.15 |
0.025 |
|
AUC 0.79. |
|
|
|
|
Cut point 0.38: 71% correctly classified | |||
|
Initial U-RTW, final model, N=282 |
|
|
|
| Risk groups: Final combination variable Overall p |
|
|
<0.001 |
| (pain/side-flexion, bodily distress, 4 dichotomous variables2) |
|
||
| Low |
1 |
||
| Intermediate |
3.23 |
1.24-8.40 |
|
| High |
7.94 |
3.20-19.7 |
|
| Radiculopathy1, ref. non-specific LBP |
0.82 |
0.39-1.74 |
0.611 |
| BMI in non-spec. LBP group, ref. 25 kg/m2 |
0.99 |
0.92-1.06 |
0.695 |
| Effect modification BMI: |
|
|
|
| OR(BMI radiculopathy)/OR(BMI non-specific) |
1.24 |
1.06-1.44 |
0.006 |
| Age |
1.03 |
1.00-1.06 |
0.082 |
|
AUC 0.73 |
|
|
|
| Cut point 0.25: 66% correctly classified |
The upper model with unsuccessful return to work at one year as outcome (one-year U-RTW).
The lower model with unsuccessful return to work during the year as outcome (initial U-RTW).
Adjustment for intervention group did not change the models. There was no effect modification for the final combination variable between patients with and without radiculopathy (one-year U-RTW, p=0.253, initial U-RTW, p=0.842).
1 Interpreted as the difference of return to work in two patients with and without radiculopathy, both persons 40 years old with BMI 25 kg/m2 and not different regarding other risk factors.
2 Final combination variable of pain/side-flexion (3 groups), bodily distress (4 groups) and 4 dichotomous risk factors: ‘Not convinced about return to work within 6 months’, ‘blaming the work for pain’, ‘drinking alcohol less than once/month’, ‘no home owner ship’.
43 missing values in the combination model: Pain score (9), bodily distress (19), blaming the work for pain (7), home ownership (4), drinking alcohol less than once/month (3), BMI (1).
OR: Odds Ratio. CI: Confidence interval. AUC: Area under curve