Types of Control in Acupuncture Clinical Trials Might Affect the Conclusion of the Trials: A Review of Acupuncture on Pain Management

Analgesic effects of acupuncture have been extensively studied in various clinical trials. However, the conclusion remains controversial, even among large scale randomized controlled trials. This study aimed to evaluate the association between the conclusion of the trials and the types of control used in those trials via systematic review. Published randomized controlled trials of acupuncture for pain were retrieved from electronic databases (Medline, AMED, Cochrane libraries, EMBASE, PsycINFO, Clinicaltrials.gov, and CAB s) using a prespecified search strategy. One hundred and thirty-nine studies leading to 166 pairs of acupuncture-control treatment effect comparisons (26 studies comprised of 53 intervention-control pairs) were analyzed based on the proportion of positive conclusions in different control designs. We found that treatment effects of acupuncture compared with nontreatment controls had the highest tendency to yield a positive conclusion (84.3%), compared with nonneedle-insertion controls (53.3%). Whereas with needle-insertion controls, the lowest tendency of positive conclusions was observed (37.8%). Consistently, in studies reporting successful blinding, a higher tendency of positive findings on the treatment effect of acupuncture was found in the noninsertion sham controls compared with that in the insertion sham controls. We conclude that the type of control is likely to affect the conclusion in acupuncture analgesic trials. Appropriate control should be chosen according to the aims of studies.