Nadine Foster, Keele University, UK

Subgrouping in back pain is the holy grail of back pain research. guidelines at the moment recommend a diagnostic triage. Despite this approach there has been no reduction in prevalence. Clear trends in high quality RCTs that there is mild effect with no difference between interventions. When we comparewhat we have to offer patient sthere are no differences and when we compare what we do with normal GP care there are small improvements.Why? Simply the natural course of these conditions, available treatments are simply not very good, heterogeneity of patients and treatment effects.

It is the heterogeneity of patients and treatment effects that Nadine will talk about.  Lots of high quality RCTs  but which person will get better with which treatment is unanswered.  arguments for subgrouping: current system of diagnostic triage is inadequate, we know clinicians believe in subgroups, promising early data, been identified as a research priority.  There several approches to subgroupng:

1. To provide more homogeneous groups: pathology, prognosis, treatment responsiveness
2. Statistical approaches
3. Clinical judgement approaches

Irrespective of these approaches the idea of sugrouping is a form of measurement.

Arguments about subgrouping:

• subgroups are not supported by data
• casual homogenetiy does not imply prognostic homogenity or treatment responsiveness
• recent guidelines for LBP do not recommend subgrouping patients with NS-LBP.  Why? Due to lack of evidence.

What are the key features of a robust approach to subgrouing?

• Plausible
• Exhaustive
• Mutually exclusive in classification
• Reliable
• Clinically useful
• Simple

What study designs and analyses are the most appropriate? (Hancock et al, 2009)

• investigate treatment effect modifiers in RCT
• limit the analyses to small number of subgroups
• use tests of interactions
• use larger sample sizes
• treat the findings with caution if the main effect of treatment is small
• externally validate (again and again …)

Nadine has been researching subgrouping for LBP in primary care.  Her investigations include the development of the STarT Back Screening Tool and trials studying this.  They are now working on the IMPACT Back study.

Subgrouping approaches have along way to go  and we need well designed clinical studies and programmes.

Read Nadine Foster’s biography

View abstract on conference website

Abstract

Low back pain is a common, disabling condition with high personal and economic costs. Despite available guidelines for practice, there have not been tangible reductions in the population prevalence of back pain or its serious long-term consequences. One reason for this, that has received increasing research attention, is that the ‘one size fits all approach advocated by many guidelines fails to target treatments at patients who might benefit from them most, thus diluting their potential benefits.

Systematic identification of key obstacles to recovery in primary care back pain patients from high quality epidemiological studies can inform the development of early, targeted interventions. Indeed, maximising the potential for optimally targeted interventions is predicated on better understanding of the prognostic factors that are causally related to clinical outcome and identifying which are a) most predictive of outcome and b) most likely to be modifiable in primary care. Only then can closer matching of treatments to patient characteristics be a clinical reality.

Using specific examples drawn from recent research within the Arthritis Research Campaign National Primary Care Centre at Keele University in the UK, and other studies, this presentation will provide an overview of subgrouping approaches under investigation, provide new evidence about the predictive strength of obstacles to recovery and share experience from studies that focus on translating subgrouping approaches into workable sytems in primary care clinical practice.

Clinical Take Home Messages:

1. Although many factors are suggested to be important obstacles to recovery, only a few are clearly distinctive, in that they independently predict back pain-related disability in primary care consulters.
2. The results challenge some assumptions regarding the key obstacles to recovery in this population and will help focus future targeted interventions.
3. The challenge is to translate this knowledge about the most predictive obstacles to recovery in primary care into workable subgrouping approaches for busy primary care practice, targeted interventions and improved outcomes for patients.

Acknowledgements: Research support from the Arthritis Research Campaign (arc), the National Institute of Health Research (NIHR) and the Health Foundation. Nadine Foster is funded by a Primary Care Career Scientist Award from the NIHR in the UK.

Nadine E Foster. Subgrouping patients with low back pain in primary care: are we getting any better at it? Manual Therapy, 2009 Oct; 14(5):S1-S54