Abstract
BACKGROUND: Sham acupuncture is a widely accepted control in acupuncture clinical trials. Given the nature of acupuncture, it is warranted to assess the blinding of sham-controlled trials. Despite the sham acupuncture design having been widely used, the overall blinding of sham acupuncture and the characteristics of blinding assessment in acupuncture trials are unclear. This research aims to assess the blinding status of acupuncture clinical trials and explore the blinding assessment characteristics in acupuncture trials. METHODS: This meta-analysis included all the acupuncture clinical trials published in English that performed blinding assessments and reported the results. We searched PubMed, Embase, and Web of Science for randomized controlled trials (RCTs) from inception to April 2024. The primary outcome is Bang's Blinding Index (Bang's BI) and 95% credibility interval (CrI) was pooled using a Bayesian hierarchical model. The study adheres to the PRISMA guidelines. RESULTS: Sixty-four eligible studies published from 1999 to 2024 were included. The mean of Bang's BI was - 0.24 (95% CrI - 0.34 to - 0.14, tau(2) = 0.13) for the sham acupuncture group and 0.41 (95% CrI 0.32 to 0.49, tau(2) = 0.10) for the verum acupuncture group. The characteristics of blinding showed that 62.50% of the trials had a Bang's BI greater than 0 in the verum group and less than 0 in the sham group; in 28.15% of the trials, the Bang's BI was greater than 0 in the verum group and greater than 0 in the sham group. Subgroup analysis revealed that area, number of research centers, treatment sessions, acupoints number, and evaluation timepoint can influence blinding results. CONCLUSION: Overall blinding status in current acupuncture clinical trials shows a majority correctly guessing for the verum group and opposite guessing for the sham group. However, in some acupuncture trials, the blinding of sham acupuncture might be compromised. Factors such as the Asian population, penetrating sham needling, and querying participants about their group assignment during the study increase the risk of unblinding and warrant careful consideration in sham acupuncture control design. Furthermore, researchers should closely monitor the blinding status of sham acupuncture and transparently report details of blinding assessments. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42023403595.