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Acupuncture for back pain: a meta-analysis of randomized controlled trials |
Ernst E, White A R |
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Authors' objectives To perform a meta-analysis of trials of acupuncture for the treatment of back pain.
Searching The following databases were searched: MEDLINE from 1969 to 1996, the Cochrane Controlled Trials Register (Issue 1, 1997), and CISCOM (November 1996), a database specialising in complementary medicine, including much of the "grey literature", such as unpublished studies and conference reports. Searches were performed using the keywords acupuncture, electroacupuncture, and backache and textword searches for the above terms together with low back pain and lumbago. The authors' files of published articles were screened and several experts in different countries were invited to contribute published studies on the topic. The bibliographies of all articles retrieved together with reviews of acupuncture treatment of pain were reviewed for further references. Authors of articles published in the past 5 years (1992 to 1997) were contacted and asked to provide information of any other articles they were aware of. Authors of abstracts were contacted and asked to provide the full reports. Articles published in English, German, Spanish, Italian, or Polish language were included.
Study selection Study designs of evaluations included in the reviewOnly randomised controlled trials (RCTs) were included. Trials in which one form of acupuncture was compared with another were excluded.
In 9 studies, outcomes were measured only at the end of treatment, and the remaining 3 studies used follow-up periods of 8 weeks, 12 weeks, and 6 months.
Specific interventions included in the reviewAcupuncture (in which dry needles were inserted into the skin) for the treatment of any type of back pain in humans. In 3 studies, conventional acupuncture points were not used; two researchers inserted needles into trigger points by tenderness and one placed needles superficially over trigger points. Recognised acupuncture points were used in the remaining 9 studies.
Participants included in the reviewHumans with any type of back pain. In 2 studies, patients were recruited after admission to hospital, either for a course of rehabilitation or for management of acute back pain. Patients were recruited via media advertisements in 1 study. In the remaining 9 trials, patients were recruited from hospital outpatient departments. In 4 studies, patients who were unresponsive to conventional therapy were included, and in the remaining 8 studies the included patients were described as having chronic back pain. Patients who had undergone back surgery were excluded in 2 studies and included in 1 study; 9 reports did not specify history of back surgery as a study criterion. Treatment settings were conventional health service premises in 11 studies and a dedicated acupuncture clinic in 1 study.
Outcomes assessed in the reviewOutcomes (in terms of number of patients improved in each group) included: evaluator's rating of change, pain, range of movement, global assessment by 2 physicians, pain score (combined patient and evaluator rating), pain and work status, VAS for pain, VAS for pain (>33% relief), VAS for pain and disability plus physician's assessment (return to work), patient assessment of improvement, activity related to pain, mobility, verbal descriptors of pain.
How were decisions on the relevance of primary studies made?The authors do not state how the papers were selected for review, or how many of the authors performed the selection.
Assessment of study quality The quality of the studies was assessed by a modification of the method described by Jadad et al. (see Other Publications of Related Interest no.1). Points were awarded in three categories: randomisation (2 points), blinding (2 points) and description of drop-outs and withdrawals (1 point). Second, points up to a maximum of 2 were awarded for each study according to the adequacy of the treatment used. Consequently the maximum quality assessment score was 7. Studies were rated on the three categories by two investigators. There was no indication whether or not this process was performed independently. The adequacy of acupuncture treatment used was assessed by blinded experts. For this purpose, an extract was prepared for each study containing only details of patients and interventions, translated into English if necessary. All means of identification were removed. Six experienced medical acupuncturists involved in both clinical practice and in teaching studied these extracts and rated the adequacy of acupuncture in each trial on a visual analogue scale (VAS) that consisted of a 100-mm line. The left end of the line was labelled "complete absence of evidence that the acupuncture was adequate" and the right end was labelled "total certainty that the acupuncture was adequate". Two points were awarded for mean VAS scores of more than 66, one point for scores between 33 and 66, and zero points for scores less than 33 mm.
Data extraction Data were extracted independently by two authors in a predefined, standardised manner. Differences were settled by discussion.
For each trial, numbers of patients in experimental and control groups who were objectively rated as improved or who had returned to work were obtained. Where objective measures were not available, subjective ratings were used. Where more than one outcome measure was reported in this way, the least and most favourable results were extracted for separate evaluations. Where necessary, letters were sent to authors requesting these data.
Methods of synthesis How were the studies combined?For each trial, the total numbers of patients included in each group and the numbers whose symptoms had improved were entered into tables for comparison. The odds ratio for each trial was calculated. Studies were weighted according to their inverse variance. A combined odds ratio for all the trials in the comparison was calculated, using the random-effects model of DerSimonian and Laird (see Other Publications of Related Interest no.2). Confidence intervals (CIs) were calculated from the sums of the individual variances, and were set at 95%. The primary meta-analyses combined all studies that contained data in the appropriate form.
How were differences between studies investigated?Tests for heterogeneity were performed using the chi-squared test.
The primary meta-analysis was performed using the data that were least favourable to acupuncture. A sensitivity analysis was performed by repeating this meta-analysis using the most favourable data.
Further meta-analyses were performed to compare subsets of trials that were combined according to particular features: blinding, length of follow-up, adequacy of acupuncture, use of formula acupuncture or electrical stimulation, and number of treatment sessions.
Results of the review In the abstract, the authors state that 12 trials were suitable for meta-analyses. However, in the results section, the authors state that 9 studies, comprising a total of 377 patients were included in the meta-analyses.
Quality assessment scores ranged from 1 to 5 (out of a maximum of 7). A funnel plot was presented to test for publication bias, but the authors concluded that there were too few studies to determine whether publication bias had influenced the result of the meta-analysis.
The odds ratio of acupuncture compared to control was 2.3 (95% CI: 1.28, 4.13). There was no significant heterogeneity between studies (chi squared = 12.58, 8 df, p>0.1).
In three studies, the outcome was markedly more positive than in the remainder. These studies had no uniformity of inclusion criteria, acupuncture approach, setting, or end points that could account for the divergence. Alternative (more favourable) outcome data were available in 1 study, yielding a new OR for all studies combined of 2.54 (95% CI: 1.32; 4.88).
Subgroup analyses: For the four sham-controlled evaluator-blinded studies, the odds ratio was 1.37 (95% CI: 0.84, 2.25). The results were not meaningfully affected by length of follow-up, quality of acupuncture, type of acupuncture, or number of sessions.
Authors' conclusions The combined result of all studies shows acupuncture to be superior to various control interventions. The combined results of 4 sham-controlled, evaluator- blinded studies did not show acupuncture to be superior to placebo.
CRD commentary The review focuses on a well defined question. A thorough search was undertaken, including an attempt to identify unpublished and grey literature. Sufficient details of the individual studies were presented.
No participant inclusion criteria were stated, so there was some variation in terms of how participants were recruited, whether or not they were responsive to conventional therapy, and whether they had undergone back surgery. The validity of included studies was assessed, but it is not clear whether this was done independently by two reviewers. Primary studies evaluating different outcomes were combined.
The conclusions follow from the results. However, both should be interpreted with caution, because, as the authors point out, the trials included in this analysis are heterogeneous in terms of study population, type of acupuncture used, outcome measure used, and length of follow-up. They also note that in most studies, the follow-up period was inadequate.
Implications of the review for practice and research Practice: The authors do not state any implications for practice.
Research: The authors suggest that further studies are required to conclude with certainty whether acupuncture has specific effects in addition to its non-specific effects. They also suggest that future research could evaluate the adverse effects of both acupuncture and spinal manipulation, and that the relative cost-effectiveness of all major treatments for back pain should be established.
Bibliographic details Ernst E, White A R. Acupuncture for back pain: a meta-analysis of randomized controlled trials. Archives of Internal Medicine 1998; 158(20): 2235-2241 Other publications of related interest 1. Jadad AR, Moore RA, Carroll D, Jenkinsen C, Reynolds DJM, Gavaghan DJ, et al. Assessing the quality of reports of randomised clinical trials: is blinding necessary? Control Clin Trials 1996;17:1-12. 2. DerSimonian R, Laird N. Meta-analysis in clinical trials. Control Clin Trials 1986;7:177-88.
This additional published commentary may also be of interest. Akupunktur bei ruckenschmerzen. Forsch Komplementarmed 1999;6:154-7.
Indexing Status Subject indexing assigned by NLM MeSH Acupuncture Therapy; Back Pain /therapy; Humans; Randomized Controlled Trials as Topic; Treatment Outcome AccessionNumber 11998009712 Date bibliographic record published 30/04/2000 Date abstract record published 30/04/2000 Record Status This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn. |
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