1. Centralization Which treatment for whom when? LBP forum 2012 Tom Petersen, PT, PhD Back Center Copenhagen Denmark

2. Subgroups Is it possible to identify particular subgroups of patients with LBP that would benefit the most from specific types of exercises?

3. Wash out effect Foster et al. 2011

4. Subgroup designs overview Prognostic factors Single group design. Hypothesis generating. All pt.s is analyzed as if they received one treatment. Not possible to differentiate beween prognostic factors and effect modifiers. Treatment effect modifiers Two group designs. Hypothesis testing. Single subgroup RCT: Is treatment effective in pre-specified group? Two-group plus subgroup covariate RCT: Are outcomes for a subgroup receiving a particular treatment (compared to control) better than for patients not in subgroup that receive same treatment? Multi-arm subgroup system RCT: Are outcomes for a range of treatments better if those are matched to a specific subgroup, than if same treatments are randomly given to patients? Kent et al. 2010

5. Prognosis - Single group designs Directional preference Review based on one study: Not a useful prognostic predictor of functional disability in patients with mixed duration of symptoms treated with McK-method and manipulation. Centralization Review based on 23 studies: Useful predictor in acute, subacute, and chronic patients treated with McK- method, CBT, strengthening, light mobilisation, or manipulation. However, lack of prediction in three studies of predominantly subacute patients. May et al. 2012 in press

6. Effect modification + Subgroup - Subgroup Treatment effect modification _ AB AB Prognostic effect Treatment effect Difference in treatment effect Kent et al. 2010

7. DP - Two group designs

8. Centralization - Two group designs

9. Conclusions – Effect modification Directional preference Conflicting evidence regarding short term effect of McK vs manipulation in patients with acute/subacute LBP. Low evidence for short term effect of McK vs strengthening exercises in patients with mixed duration of symptoms. Clinically important. Centralization Very low evidence for long term effect of McK vs manipulation in patients with acute LBP. Clinically important. Moderate evidence for long term effect of McK vs manipulation or strengthening exercises in patients with mixed duration or chronic LBP. Questionnable clinical importance in chronic LBP. Peripheralization a stronger effect modifier?