Title: The Effectiveness of Participant Blinding of Non-Penetrating Sham/Placebo Acupuncture in Clinical Trials: A Systematic Review with Meta-Analysis

Abstract Background: Acupuncture clinical trial is important to evaluate the efficacy of acupuncture. However, it is challenging to achieve effective blinding due to the nature of acupuncture. A standardised placebo control method of acupuncture has yet to be established. The study focuses on the non-penetrating sham acupuncture because it eliminates the placebo effect and generates lesser physiological responses. The study aims to evaluate and compare the participant blinding effectiveness of non-penetrating sham acupuncture devices, and analyse the factors which may influence the participant blinding.Methods: The study followed the PRISMA guidelines. An electronic search was conducted on PubMed, Ovid and CNKI up until 1st of October 2020 to include English and Chinese randomised controlled trials which evaluated the awareness on the type of acupuncture (real or sham) in any population who received acupuncture. Data screening, data extraction and quality assessment were done independently by two researchers and discrepancies were sorted out via discussion with a co-researcher. Data analysis was performed using RevMan 5.4.1.Results: 34 full-text articles had been included in the systematic review and meta-analysis. The quality of the studies ranged from moderate to good. Generally, non-penetrating sham acupuncture devices were effective in blinding participants in clinical trials. The foam device demonstrated a better blinding effect, followed by Streitberger, Park and Takakura devices. Sham needles with no skin contact could not blind the participants successfully. Naive, experienced, healthy and diseased participants all could be blinded using non-penetrating sham acupuncture devices but naive and healthy participants could be blinded comparatively easily. Acupoints from different regions could achieve blinding, however, the acupoints on the back could blind the participants more easily compared to the other areas.Conclusion: Non-penetrating sham acupuncture devices are valid placebo control for acupuncture clinical trials. The foam device has a better blinding effect, followed by Streitberger, Park and Takakura devices. Recruiting naive healthy participants and choosing acupoints from the back can achieve better blinding effects in the participants.