Blinding in acupuncture research: a systematic review of randomized controlled trials for pain using a sham acupuncture control

Objective: To study the various methods and levels of blinding in acupuncture research. Data sources: Reference lists of the most recent systematic review of acupuncture on pain, systematic search of MEDLINE from 1966 to August 2000, CINAHL from 1982 to August 2000, and HealthSTAR from 1975 to August 2000.

Study selection: Randomized studies were included if they evaluated the effectiveness of acupuncture in painful conditions using a blinded design.

Data extraction: The hard copy of each of the eligible studies available was reviewed. The following information was extracted: name of first author, publication year, study design, blinding testing, treatment sham group received, and the outcome measures.

Data synthesis: There were 19 studies identified. They were described as ‘double blinded’ by the authors, referring to blinding of patients and evaluators. Sixteen studies did not perform any blinding testing after the treatments were over. Only three studies provided information that the blinding of patients was successful. These three studies used different questionnaires to assess the success of blinding. There was no study that evaluated the success of blinding of treatment evaluators. Also, no study attempted blinding of the treating acupuncturists.

Conclusions: Proper blinding of patients and evaluators is possible in acupuncture research and many different techniques of proper blinding exist. Assessment of blinding is a critical aspect of any sham or placebo controlled trial and should be routinely incorporated into the design of such trials of acupuncture.