Meta-Analysis: Acupuncture for Low Back Pain

To the Editor,

We thank Dr. Shekelle for the opportunity to further clarify our methods, data, and conclusions. Firstly, we calculated standardized mean differences using post-treatment mean values and standard deviations for each group. For the Liebing study only, we used baseline standard deviations because post-treatment standard deviations were not reported (1). We pre-specified a comparison of post-treatment scores, which may have an advantage over between group changes among trials in which standard deviations of differences in changes are incompletely reported (1). We recognize that between group change scores and post-treatment scores may result in different standardized mean differences when there are baseline differences between the groups (as occurred in the Liebing study). To address the possibility that between group changes and final value analysis methods might result in different effect sizes, we have recalculated our effect sizes comparing sham acupuncture with acupuncture, using between group changes and the following assumptions. The Molsberger trial did not report standard deviations of between group changes, or any statistics that would allow us to calculate these (2). For the 4-week data from this trial, we assumed a within subject pre-post correlation of 0.5. For the Mendelson trial, the authors appear to have reported two different t values in the Abstract (t=.52) and in a footnote to Table IV (t=.34) (3). Because of our uncertainty over which, if either, of these t values was correct, we have performed three different between group changes meta-analyses, the first using the t=.34, the second using the t=.52, and the third assuming a conservative pre-post correlation of 0.5. Recalculation using our estimated between-group change scores results in slightly smaller effect sizes (between .51 and .57) and wider confidence intervals that were still statistically significant.

Secondly, for the von Mencke trial, we used the outcome data from immediately after the end of the first treatment period (i.e., point less than 6 weeks, and closest to 3 weeks following end of treatment) (4). There were no drop-outs or cross-overs at this measurement point; data shown in Table XII of the trial report suggests that all 65 patients were available for analysis at this time point. We have used a second independent German translation to confirm the accuracy and appropriateness of the data we used. Thirdly, we took into account whether trials evaluated credibility of the sham by using a modified Jadad scale which substituted the credibility testing item for a randomization stated (Y/N) item. This substitution had the effect of reducing all trials' scores by one point on the five-point quality scale. Although we evaluated the credibility testing item, and penalized the quality scores of all trials in our sample by doing so, we believe that the validity of this item is unclear and warrants further study. Lastly, we think that both our original analyses based on post-treatment mean values and our additional analyses based on between group changes that were presented above support the following conclusion. Current preliminary data suggest that acupuncture may be more effective than inactive controls for providing short-term relief of chronic low back pain.

Eric Manheimer University of Maryland School of Medicine [email protected]

References

1. Deeks JJ, Higgins, JPT, Altman DG, editors. Analysing and presenting results. In: Higgins JPT, Green S, editors. Cochrane Handbook for Systematic Reviews of Interventions 4.2.4 [updated March 2005]; Section 8. http://www.cochrane.org/resources/handbook/hbook.htm (accessed 23 July 2005)..

2. Molsberger AF, Mau J, Pawelec DB, Winkler J. Does acupuncture improve the orthopedic management of chronic low back pain - a randomized, blinded, controlled trial with 3 months follow up. Pain 2002;99:579-87. [PMID: 12406534]

3. Mendelson G, Selwood TS, Kranz H, Loh TS, Kidson MA, Scott DS. Acupuncture treatment of chronic back pain. A double-blind placebo- controlled trial. Am J Med 1983;74:49-55. [PMID: 6217745]

4. von Mencke M, Wieden TE, Hoppé M, Pörschke W, Hoffmann O, Herget HF. Akupunktur des schulter-arm-syndroms und der lumbalgie/ischialgie - zwei prospektive doppelblind-studien (Teil 2). Akupunktur Theorie und Praxis 1989;5:5-13.

Eric Manheimer, MS, Center for Integrative Medicine, University of Maryland School of Medicine, 2200 Kernan Drive, Kernan Hospital Mansion, Baltimore, MD 21207

Adrian White, MD, BM, BCh, Peninsula Medical School, ITTC Building, Tamar Science Park, Plymouth PL6 8BX, United Kingdom

Edzard Ernst, MD, PhD, Complementary Medicine, Peninsula Medical School, 25 Victoria Park Road, Exeter, Devon EX2 4NT, United Kingdom

Patricia Langenberg, PhD, Department of Epidemiology and Preventive Medicine, University of Maryland School of Medicine, Suite 109 Howard Hall, 660 W. Redwood Street, Baltimore, MD 21201

Conflict of Interest:

Adrian White is employed part-time by the British Medical Acupuncture Society as journal editor.

To the editors:

With regard to the paper "Meta-analysis: acupuncture for low back pain" by Manheimer and colleagues (1), I believe the authors may have overestimated the principal findings of their study, the short-term effects on pain for acupuncture compared to sham. First, in Figure 1, Manheimer and colleagues reported a larger effect size than was originally reported in the Leibing study (2). Secondly, they included a study by von Mencke and colleagues (3) that had several methodologic shortcomings, including that outcome assessments appear to be based on only 11 of the 30 patients randomized to receive sham acupuncture, as 63% of the sham group ended up receiving real acupuncture and therefore could not be included in the sham vs. acupuncture comparison. Thirdly, none of the four studies included in the sham pooled result tested the credibility of their sham, usually accomplished by asking patients to guess whether or not they received real or sham acupuncture. Without an assessment of the credibility of the sham, we cannot conclude that the study was effectively "blinded," and the possibility of expectation bias cannot be excluded. Excluding the study by von Mencke and using the effect size estimate of 0.27 reported in the study by Leibing yields a pooled effect size for the remaining three studies of 0.425 (95% CI 0.19, 0.66). This effect size translates into a change in pain intensity of 10.6 mm on a 100 mm VAS pain scale, which is at the threshold of what is considered "clinically significant". It probably represents an "upper bound" on the estimate of efficacy of acupuncture in these studies, because the possibility of expectation bias cannot be excluded. Therefore, I believe based on these data it is premature to conclude that "acupuncture effectively relieves chronic low back pain." Before such a conclusion can be reached, better quality RCTs are necessary that report statistically and clinically significant benefits for acupuncture compared to a demonstrably credible sham therapy.

Paul Shekelle Rand Corporation [email protected]

References: 1. Manheimer E, White A, Berman B, Forys K, Ernst E. Meta-analysis: acupuncture for low back pain. Ann Intern Med. 2005;142:651-63.

2. Leibing E, Leonhardt U, Koster G, Goerlitz A, Rosenfeldt JA, Hilgers R. Et al. Acupuncture treatment of chronic low-back pain"”a randomized, blinded, placebo-controlled trial with 9-month follow-up. Pain. 2002;96:189-96.

3. von Mencke M, Wieden TE, Hoppe M, Porschke W, Hoffmann O, Herget HF. Akupunktur des Schulter-Arm-Syndroms und der Lumbalgie/Ischialgie"”Zwei Prospective Doppelblind-Studien (Teil 2). Akupunktur Theorie und Praxis.

Conflict of Interest:

None declared