Sham control methods used in ear-acupuncture/ear-acupressure randomized controlled trials: a systematic review

Ear-acupuncture/ear-acupressure (EAP) has been used for a range of health conditions with numerous randomized controlled trials (RCTs) investigating its efficacy and safety. However, the design of sham interventions in these RCTs varied significantly. This study systematically reviewed RCTs on EAP for all clinical conditions involving a number of sham EAPs as a control intervention. The review is guided by the Cochrane Handbook for Systematic Reviews of Interventions 5.1.0 and investigated the types and differences of sham EAP interventions. Four electronic English databases (The Cochrane Library, PubMed, Embase, CINAHL®) and two Chinese databases (CQVIP, CNKI) were searched in December 2012 and 55 published RCTs comparing real and sham EAP for any clinical condition were included. Characteristics of participants, real and sham interventions, and outcomes were extracted. Four types of sham methods were identified. Among the 55 RCTs, 25 studies involved treatment on nonspecific ear acupoints as the sham method; seven studies used nonacupoints on the ear; nine studies selected placebo needles or placebo ear-acupressure on the same ear acupoints for the real treatment; 10 studies employed pseudo-intervention; and five studies combined two of the above methods to be the sham control. Other factors of treatment such as number of points, treatment duration, and frequency also varied greatly. Risk of bias assessment suggests that 32 RCTs were "high risk" in terms of participants blinding, and 45 RCTs were "high risk" in terms of personnel blinding. Meta-analysis was not conducted due to the high clinical heterogeneity across included studies. No relationship was found between the sham designs and efficacy outcomes, or between the sham types and dropout rate. No solid conclusion of which design is the most appropriate sham control of EAP could be drawn in this review.