Weak evidence was found of an effect of acupuncture care on non-specific low back pain at 12 months, but stronger evidence of a small benefit at 24 months.
On the basis of pilot data our study was designed to detect a larger difference of 10 points, which was not achieved at either 12 or 24 months. A difference of at least five points in the mean score of the SF-36 bodily pain dimension is, however, considered to represent a clinically worthwhile benefit9
and a difference of between five and nine points can be viewed as a moderate effect.19,20
In this study the magnitude of the effect extends to eight points at 24 months, a difference between groups of about 10%-15% of the final pain score in the control group, and achieves statistical significance. We found no evidence of functional improvement. Other patient relevant outcomes included patient satisfaction with acupuncture care, reduced concerns about back pain, and reduced use of analgesics.
One limitation of our study is the possibility of an effect of clustering by practitioner (six acupuncturists delivered the treatment) on the statistical significance of the outcome. In this case, cluster analysis made little difference to the primary outcome of bodily pain at 12 and 24 months. Sensitivity analysis taking into account baseline covariates increased the intervention effect but did not alter the main results. Groups were well balanced at baseline with the exception of 11 patients who described themselves as permanently unable to work because of low back pain, all of whom were in the acupuncture arm. Excluding these patients increased the estimated effect of acupuncture at 12 months.18
Secondary outcome measures showed mixed effects. Those measuring the effect of pain on daily living did not show a significant acupuncture effect at 12 or 24 months. Detailed analysis of item responses to the SF-36 and Oswestry pain disability index could help to identify the specific effect of acupuncture on low back pain. Patients in the acupuncture group reported a substantial reduction in concerns about their back pain that was not observed in the usual care group. A qualitative investigation is indicated to explore the meaning to patients of this reduction in worry, its relation to patient coping strategies, and its implications for the care and management of this group of patients.
We evaluated a package of care and cannot isolate the components of acupuncture treatment that are associated with the outcomes observed in the acupuncture group. Beyond the needling itself, several aspects of acupuncture care in this trial could contribute to its observed effectiveness, including the individualising of treatment,21
the interaction effect generated by the combination of specific effects,22
the practitioner's skills at developing good therapeutic relationships,23
process benefits such as protected time and attention from the practitioner,24
and the widely reported relaxing experience of the treatment itself.25
An open pragmatic trial avoids the potential problems associated with using sham acupuncture as the control.26
Such a design may, however, be vulnerable to confounding or bias owing to prior patient beliefs about how acupuncture might help, especially when using subjectively assessed outcome measures, such as perceived pain. Positive patient beliefs about acupuncture have been cited as a possible mechanism for non-specific effects observed in acupuncture trials.27,28
Our exploratory analysis does not seem to support this hypothesis. Patients in the acupuncture group with a prior positive belief in the effectiveness of acupuncture fared little better than those randomised to usual care. In contrast, patients with neutral prior belief gained relatively more benefit from acupuncture care. In addition, positive expectations of improvement in back pain seem to reinforce the effect of acupuncture care.
Overall, 76% of our participants were followed up at 24 months. We detected no difference between groups in the known characteristics of missing cases, and sensitivity analysis substituting missing values with prior observations did not change the main findings, but the effect of the missing data is unknown. The strengths of our study were the pragmatic randomised design, successful patient recruitment, wide eligibility criteria, and a non-restrictive treatment protocol that allowed acupuncturists to treat patients as they would do in everyday practice.29
The acupuncturists were selected through reproducible criteria, and the ratio of six practitioners to 16 general practices is similar to the national ratio of acupuncturists registered with the British Acupuncture Council to general practices. All these factors enhance the relevance of the results by replicating conditions under which an acupuncture service might be offered and used in NHS primary care.
Recruitment to the trial suggests that general practitioners are able to identify suitable patients for referral. In a retrospective survey, participating general practitioners estimated that they had identified about half the eligible patients seen in the recruiting period. No evidence was found of reluctance by general practitioners to refer patients for acupuncture. The results from this trial on the safety and possible benefits of acupuncture care for low back pain will be of interest to general practitioners who are asked about such treatment by their patients, and to patients considering acupuncture care outside the NHS. However, the generalisability of our findings rests on the assumption that participating acupuncturists, general practitioners, and patients in York are similar to those found elsewhere.
Studies of interventions for low back pain are particularly susceptible to effects arising from a regression to the mean; patients will tend to seek help at the point when the pain is at its worst or least bearable, and the clinical course of the condition is that the pain will reduce substantially for most people, with or without treatment. Commentators have indicated a need for more evidence of longer term effects, particularly related to discrete, short term interventions delivered early in an episode of persistent low back pain, that result in a reduction in recurrence and persistence of symptoms.30
Our study contributes evidence for a short term acupuncture intervention compared with usual general practitioner care for non-specific low back pain. Further clinical research is indicated to investigate the optimum timing for such an acupuncture treatment package, and to assess the value of repeated courses of acupuncture for patients experiencing recurrent episodes of low back pain.
To address the question of whether the clinical benefits observed justify the cost of the therapy, we report the cost effectiveness of this intervention in the accompanying economics paper.8
What is already known on this topic
Non-specific low back pain is typically a recurrent condition associated with high health and social costs
Many people with back pain seek acupuncture treatment; however, evidence for long term effectiveness is sparse
What this study adds
Weak evidence was found of an effect of acupuncture care on non-specific low back pain at 12 months, but stronger evidence of a small benefit at 24 months
Referral to a qualified acupuncturist seems safe and acceptable to patients with low back pain