A phenomenon well-known in academic circles is called publication bias. This is where negative or equivocal findings are not published in favour of studies where results are positive. Today I’m going to counter this bias by discussing a study in which physiotherapy based on treatment classification with either graded exposure or graded activity was compared with treatment alone – and no difference in the long term was found.
Pain-related anxiety and avoidance has been an area of study in the development of chronic disability from pain for some years now. Vlaeyen and colleagues have been influential in developing this model and studying treatments that may reduce the disability associated with pain-related activity avoidance.
This study by George, Zeppieri, Cere et al. (2008) looks at a clinical trial comparing the effectiveness of treatment-based classification (TBC) physical therapy alone to TBC augmented with graded activity (GA) or graded exposure (GX) for patients with acute and sub-acute LBP.
‘Graded exercise and graded exposure are specific behavioral interventions that dose exercise and activity parameters on factors other than pain intensity. Briefly, graded exercise uses a quota system to progress subjects’ therapeutic exercise and activity. In contrast, graded exposure hierarchically exposes subjects to specific situations of which they are fearful by starting with exercise or activity that elicits minimal amounts of fear, and then gradually increasing to situations that elicit larger amounts of fear.’
Primary outcomes for this clinical trial were disability and pain intensity, and the secondary outcomes were fear-avoidance beliefs, pain catastrophizing, and physical impairment.
Participants: Consecutive patients seeking treatment for LBP at three participating University of Florida affiliated clinics. Quebec Task Force on Spinal Disorders classification
- 1a or 1b (acute or sub-acute LBP without radiation below the gluteal fold)
- 2a or 2b (acute or sub-acute LBP with proximal radiation to the knee)
- 3a or 3b (acute or sub-acute LBP with distal radiation below the knee)
The ability to read and speak English, and aged between 15 and 50.
Participants were excluded if they were pregnant, had osteoporosis, and were not classified into the three groups above.
A balanced pre-determined randomisation process with stratification into the three clinics was used to allocate participants to treatment groups, and providers were not aware of the randomisation order.
Measures: Oswestry Disability Questionnaire, Numeric rating scale, Fear avoidance beliefs questionnaire, Pain catastrophising scale and a physical impairment scale were completed.
Therapists were experienced, selected on the basis of their scores for belief in the treatments they were to use, and completed a training module before the study on the techniques and documentation to be used.
Treatments: A treatment-based classification system originally developed by Delitto et al (1995). TBC is a standard system that assists clinicians in identifying LBP sub-groups and matching appropriate treatment consisting of specific exercise, manipulation or mobilization, lumbar stabilization, or traction.
‘Graded activity was developed using an activity quota determined by having the patient perform standard aerobic and therapeutic exercises to pain tolerance. The parameters (duration, intensity, and frequency) used to reach pain tolerance were then established as the activity quota. These were then increased by 10% in duration and/or frequency in subsequent sessions.‘
Graded exposure was developed using the protocol previously developed by Vlaeyen and colleagues. Feared activities were assessed with a standard questionnaire that listed 10 activities subjects with LBP are commonly fearful of, for example, lifting, carrying, twisting, and bending. Therapists then selected the two items ranked as most fearful for implementation in graded exposure. These activities were progressed exposure therapy principles and standardized to address fears related to position, intensity, frequency, and duration as appropriate for a given activity.
Results: 36 participants were entered into the TBC alone group, 37 to graded activity, and 35 to graded exposure. The groups were fairly similar with the exception of differences for duration of symptoms and pain catastrophizing. Neither duration nor pain catastrophizing was significantly correlated with the primary outcome measures at the conclusion of the study.
All participants, irrespective of group, improved on scores on the ODQ. Pain intensity ratings also improved. No difference was found for either GX or GA for those with high fear-avoidance scores.
All participants had reduced fear-avoidance scores at 4 weeks, but GA participants did not show as much of a reduction at 6 months. Pain catastrophising was similarly affected at 4 weeks for all participants, the GX group did show high pain catastrophising (but this was evident before treatment was started, probably a difference between the participants rather than a treatment effect).
At four weeks, only pain intensity changes influenced overall disability scores, but fear avoidance beliefs and physical impairment were associated with reduced pain intensity and not with reduced pain catastrophising. ‘At six months GX and TBC were associated with larger reductions in fear-avoidance beliefs. Six-month reduction in disability was associated with reduction in pain intensity, while 6-month reduction in pain intensity was associated with reductions in fear-avoidance beliefs and pain catastrophizing.’
So, what does this tell us? Basically, in this group of participants, there was no real benefit from adding either graded exposure or graded activity to treatment based on Delitto’s classification (TBC).
TBC as used in this trial was conducted slightly differently from previous studies, in that empirically-derived decision rules were developed and clinical opinion was not used. As I mentioned a couple of days ago, it seems that ‘expert opinion’ can often reduce the accuracy of decision rules generated from data alone. This is a good example of a situation where ‘treatment by the rule’ worked reasonably well (but I can see this idea going down like a lead balloon in many treatment settings!).
The authors suggest that one reason their hypothesis may not have been supported was that the graded exposure process used self report rather than PHODA. ‘We utilized a pragmatic approach for identifying fearful activities because we needed a process that would minimally disrupt the clinical environment, and the shortened version of the PHODA was unavailable at the start of this trial.’
I’ve used the PHODA as my mainstay when developing a graded hierarchy with patients, because I’ve found it can be quite tiny differences between pictures in this series that evokes a response from the person. For example, there are several photographs of people lifting items from the ground – with slightly different contexts (inside, outside), load sizes (dog bowl to a heavy plant pot), and postures (bent knees, straight knees, semi squat and ‘natural’ posture). And it can be any one of these slight differences that the person responds to. Without the stimulus of the picture, it can be hard to identify just what the person is concerned about. (J Pain. 2007 Jul 12; : 17632038 (P,S,G,E,B,D) )
Another reason for no difference between the GA and GX conditions the authors suggest, is that the two treatments overlap somewhat – although they’re quite different in principle, that the person starts with a low level of activity, and progress gradually, can be somewhat similar to the person. Similarly, the authors point out ‘both approaches utilized an education approach of reducing the fear and threat associated with LBP.’ They go on to say ‘Our current data suggest that it may not be necessary to implement a formal exposure paradigm for patients with sub-acute or acute LBP if the GA component includes a variety of activities that subjects are likely to fear.’
A final reason could be that the participants came from both subacute and chronic back pain groups. The factors that initiate disability can be different from those that maintain disability – and this may be especially apparent in the subacute and chronic groups. Those with chronic pain need to focus on reducing disability, while ‘reduction of pain intensity and physical impairment remains the primary goal for patients with acute and sub-acute LBP. The novel information gained from this randomized trial is that it may not be necessary to apply GX or GA to reduce psychological variables if TBC is used.’
From this study, you can see why it can be difficult for people who are not au fait with the larger body of published data on pain-related anxiety and avoidance to decide whether or not to include a new approach into their practice. Good research articles will explore the applicability of their findings to different populations, will point out the limitations of the study design, applicability – and how it fits in with other research.
BUT, and it’s a big but, it’s really important to remember a saying a good friend told me ‘Two swallows do not a summer make’.
It’s up to YOU as a clinician to keep up with new information about conditions you treat. This can mean going outside of your usual discipline (this study is a cross-over of physical therapy and a psychological treatment approach), and it does mean reading, reading, reading. It also means suspending judgement until you’ve gathered some more information. It means becoming conversant with research methodology, and yes – even statistics!
I’ll keep blogging about topics that interest me – and sometimes I do this simply to ask myself a question, and challenge my own beliefs. Questioning is good – to assume, remember, makes an ‘ASS’ out of ‘U’ and ‘ME’.
Delitto A, Erhard RE, Bowling RW. A treatment-based classification
approach to low back syndrome: identifying and staging
patients for conservative treatment [see comments]. Phys Ther
S GEORGE, G ZEPPIERIJR, A CERE, M CERE, M BORUT, M HODGES, D REED, C VALENCIA, M ROBINSON (2008). A randomized trial of behavioral physical therapy interventions for acute and sub-acute low back pain (NCT00373867) Pain, 140 (1), 145-157 DOI: 10.1016/j.pain.2008.07.029