We'll keep this brief...
This “evidence-based study” out of the Journal of Traditional Chinese Medicine used surprisingly good methods looking at the efficacy of acupuncture for a variety of cardiac problems.
But due to fatal flaws, the majority of the details and the conclusion to this paper are irrelevant. Nevertheless it does provide some great opportunity for learning & teaching critical appraisal of the literature.
This systematic review found 21 articles that investigated acupuncture for angina. Unfortunately none of them were blinded, had allocation concealment or had sham acupuncture arms. Therefore all of the proposed benefit could easily be explained by the theatrical placebo of acupuncture. All prior good quality studies of acupuncture using proper blinding have shown it is no better than placebo.
The paper does mention these methodology issues and go so far as to say “all studies were assessed as having a high or moderate risk of bias.” Had they stopped here everything would have been fine. But they made the tragic mistake of proceeding to a meta-analysis and making ludicrous conclusions.
There are some statistical truths. No amount of analysis can remove bias from a study (simple confounding is a different matter). Nor can bias be overpowered by increasing the study size.
Put another way, they completely missed the crucial backbone of meta-analysis. If all you find is rubbish, you don’t combine it in a blender and expect a golden egg to appear. You’ve still got rubbish.
Chen J, Ren Y, Tang Y, et al. Acupuncture therapy for angina pectoris: a systematic review. J Tradit Chin Med 2012;32(4):494-501.