Lumpers, Splitters and STarTers

In recent years there have been many debates about the disappointing results from clinical trials of treatments for non-specific low back pain. One argument has been about the targeting of treatment for back pain. Many folk have argued that trials which apply a one-size-fits-all treatment fail to show a reasonable effect because amongst those who should be given that treatment there are others for whom the treatment is inappropriate and so the true effect is washed out. The proposed solution is to more effectively target treatments to specific groups of patients in trials, or only include the patients who are likely to be responders. Let’s call the people who hold this position “the splitters”.

Then there are others (myself included) who wonder if the existing evidence has ever really pointed towards sub-grouping as an explanation for the poor performance of treatments. We tend to believe the message from the existing trial evidence, that current treatments are a bit rubbish. We wonder whether subgrouping might be a case of “searching for the pony”*. We can’t really see a valid way of choosing which treatment is likely to work for whom and we are often critical of some of the attempts that have been made to identify specific responders, wondering if they might be a bit statistically “dodgy”. Certainly we don’t really feel that we are close to a diagnostic model in back pain that could guide this process. Let’s call folk like me the “lumpers”.

There are a number of ways to go about answering this question and ways in which one might try to subgroup patients. You might try to establish valid diagnostic subgroups in back pain (good luck with that), you might mine the data from existing trials to see what factors seem to predict a good outcome (a minefield of potential statistical wrongness) or you might look at the best data available on the factors which predict poor outcome and then group folk by their risk of not getting better, tailoring the amount and type of treatment to that risk. Who else thinks that’s nifty and a question worth asking?

A research team from Keele University in the UK, led by Jonathan Hill have tested just such an approach in a massive (851 participants!) and impressive RCT. This is big ambitious research: precisely the kind we need to draw reliable conclusions. The fact that Dr Hill is a physiotherapist should be pleasing to many of us. The STarT Back Trial used a tool based on established risk factors to group patients with back pain into low, medium and high risk of poor outcome and then randomised participants to care that was tailored to this risk or to standard physiotherapy care. In the tailored care group patients assessed as low risk had just one session of advice focusing on being active and exercising through a therapist, a video and a pamphlet and were only referred for more treatment at the discretion of the referring physiotherapist (kind of usual physiotherapy care), medium and high risk patients were always referred for further physiotherapy led treatment, with high risk patients specifically receiving psychologically informed treatment.

So was this the good news trial for back pain that we’ve been looking for? The results showed significant improvements in disability and pain in the intervention group overall. Those in the medium and high risk groups who received stratified care did better and those in the low risk group did no worse than those receiving standard care. An important message that arises is that for low risk patients one session of advice is not inferior to the same advice plus usual physiotherapy care. More is not always better.  On top of this the new approach seemed to cost a little less.

But there are some buts. The effects are small at the end of treatment (at 4 months around a 2 point change in disability from a baseline score of about 10 overall), and are smaller still at 1 year (around a 1 point change compared with usual physiotherapy care that is only significant in the medium risk group).The changes within the groups look more impressive but these can not be confidently attributed to the treatment. In fact you would need to treat about 10 patients for one more patient who received targeted care to achieve a “good outcome” (a 30% improvement in their disability score) at one year compared to usual physiotherapy.  In the group at highest risk of not getting better we can estimate that they would still have an average disability score of around 10/24 a year after treatment.

To be clear these are not reservations about the trial which is a real achievement. Here is evidence that sub-grouping can influence outcome, a little bit. But the benefits are modest and suggest to a grumpy lumper (or “grumper”) like myself that subgrouping, at least in this way, is not likely to make a big dent in the problem of back pain just yet.

About Neil

Neil OConnellAs well as writing for Body in Mind, Neil O’Connell is a researcher in the Centre for Research in Rehabilitation, Brunel University, West London, UK. He divides his time between research and training new physiotherapists and previously worked extensively as a musculoskeletal physiotherapist. He also tweets! @NeilOConnell

He is currently fighting his way through a PhD investigating chronic low back pain and cortically directed treatment approaches. He is particularly interested in low back pain, pain generally and the rigorous testing of treatments. Link to Neil’s published research here. Downloadable PDFs here.

*Searching for the pony

There was once a man with twin daughters, one irrepressibly optimistic, the other incurably pessimistic. He felt that neither was a good approach to life, so on their birthday he presented the pessimist with a roomful of fantastic toys and games, and the optimist with a roomful of manure and left them to it

When he came back a while later, he found the pessimist holding a broken toy, crying that sooner or later, all the rest would also break. The optimist, however, had found a shovel and was tackling the manure with gusto. When asked why she was bothering, she replied that: “With all that shit, there’s got to be a pony in there somewhere.”

(this version of the apocryphal story copied from a comment from the bad science forums by a poster “DrJG” http://bit.ly/pcSeuj )

References

ResearchBlogging.org

Hill JC, Whitehurst DG, Lewis M, Bryan S, Dunn KM, Foster NE, Konstantinou K, Main CJ, Mason E, Somerville S, Sowden G, Vohora K, & Hay EM (2011). Comparison of stratified primary care management for low back pain with current best practice (STarT Back): a randomised controlled trial. Lancet PMID: 21963002

Hancock M, Herbert RD, & Maher CG (2009). A guide to interpretation of studies investigating subgroups of responders to physical therapy interventions. Physical therapy, 89 (7), 698-704 PMID: 19465372

Wand BM, & O’Connell NE (2008). Chronic non-specific low back pain – sub-groups or a single mechanism? BMC musculoskeletal disorders, 9 PMID: 18221521