CentralizationWhich treatment for whom when?

LBP forum 2012

Tom Petersen, PT, PhD Back Center Copenhagen

Denmark

Subgroups

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

Wash out effect

Foster et al. 2011

Subgroup designs overview

Prognostic factorsSingle 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 modifiersTwo 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

Prognosis - Single group designs

Directional preferenceReview 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.

CentralizationReview 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

Effect modification

+ Subgroup - Subgroup Treatment effect modification

_

A B

A B

Prognostic effect

Treatment effect

Difference in treatment effect

Kent et al. 2010

DP - Two group designs

Centralization - Two group designs

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?